220 lines
8.5 KiB
Diff
220 lines
8.5 KiB
Diff
From: csagan5 <32685696+csagan5@users.noreply.github.com>
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Date: Fri, 30 Mar 2018 10:09:03 +0200
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Subject: getClientRects, getBoundingClientRect, measureText: add
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fingerprinting mitigation
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Scale the result of Range::getClientRects, Element::getBoundingClientRect and
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Canvas::measureText by a random +/-3/1000000th of the original value for each
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float in the returned Rect/Quad.
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Rationale is that the returned values are within the same order of magnitude
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of the floating point precision being used for fingerprinting and sufficient
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to poison the well.
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See also: http://www.gsd.inesc-id.pt/~mpc/pubs/fingerprinting-trustcom2016.pdf
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---
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third_party/blink/renderer/core/dom/document.cc | 13 +++++++++++++
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third_party/blink/renderer/core/dom/document.h | 5 +++++
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third_party/blink/renderer/core/dom/element.cc | 16 ++++++++++++++++
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third_party/blink/renderer/core/dom/range.cc | 18 +++++++++++++++++-
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.../blink/renderer/core/html/canvas/text_metrics.cc | 18 ++++++++++++++++++
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.../blink/renderer/core/html/canvas/text_metrics.h | 2 ++
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.../canvas/canvas2d/canvas_rendering_context_2d.cc | 10 +++++++++-
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7 files changed, 80 insertions(+), 2 deletions(-)
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diff --git a/third_party/blink/renderer/core/dom/document.cc b/third_party/blink/renderer/core/dom/document.cc
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--- a/third_party/blink/renderer/core/dom/document.cc
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+++ b/third_party/blink/renderer/core/dom/document.cc
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@@ -33,6 +33,7 @@
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#include "base/auto_reset.h"
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#include "base/optional.h"
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+#include "base/rand_util.h"
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#include "services/metrics/public/cpp/mojo_ukm_recorder.h"
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#include "services/metrics/public/cpp/ukm_builders.h"
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#include "services/metrics/public/cpp/ukm_source_id.h"
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@@ -722,6 +723,10 @@ Document::Document(const DocumentInit& initializer,
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}
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DCHECK(fetcher_);
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+ // add X/Y noise factors that will be used to mitigate fingerprinting
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+ shuffleFactorX_ = base::RandDouble();
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+ shuffleFactorY_ = base::RandDouble();
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+
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root_scroller_controller_ = RootScrollerController::Create(*this);
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// We depend on the url getting immediately set in subframes, but we
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@@ -787,6 +792,14 @@ Range* Document::CreateRangeAdjustedToTreeScope(const TreeScope& tree_scope,
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Position::BeforeNode(*shadow_host));
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}
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+double Document::GetShuffleFactorX() {
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+ return shuffleFactorX_;
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+}
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+
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+double Document::GetShuffleFactorY() {
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+ return shuffleFactorY_;
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+}
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+
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SelectorQueryCache& Document::GetSelectorQueryCache() {
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if (!selector_query_cache_)
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selector_query_cache_ = std::make_unique<SelectorQueryCache>();
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diff --git a/third_party/blink/renderer/core/dom/document.h b/third_party/blink/renderer/core/dom/document.h
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--- a/third_party/blink/renderer/core/dom/document.h
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+++ b/third_party/blink/renderer/core/dom/document.h
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@@ -418,6 +418,9 @@ class CORE_EXPORT Document : public ContainerNode,
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has_xml_declaration_ = has_xml_declaration ? 1 : 0;
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}
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+ double GetShuffleFactorX();
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+ double GetShuffleFactorY();
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+
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String visibilityState() const;
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mojom::PageVisibilityState GetPageVisibilityState() const;
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bool hidden() const;
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@@ -1776,6 +1779,8 @@ class CORE_EXPORT Document : public ContainerNode,
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double start_time_;
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+ double shuffleFactorX_, shuffleFactorY_;
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+
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TraceWrapperMember<ScriptRunner> script_runner_;
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HeapVector<Member<ScriptElementBase>> current_script_stack_;
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diff --git a/third_party/blink/renderer/core/dom/element.cc b/third_party/blink/renderer/core/dom/element.cc
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--- a/third_party/blink/renderer/core/dom/element.cc
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+++ b/third_party/blink/renderer/core/dom/element.cc
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@@ -1202,6 +1202,15 @@ DOMRectList* Element::getClientRects() {
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DCHECK(element_layout_object);
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GetDocument().AdjustFloatQuadsForScrollAndAbsoluteZoom(
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quads, *element_layout_object);
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+
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+ // scale all quads
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+ auto shuffleX = 1 + (GetDocument().GetShuffleFactorX() - 0.5) * 0.000003;
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+ auto shuffleY = 1 + (GetDocument().GetShuffleFactorY() - 0.5) * 0.000003;
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+
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+ for (FloatQuad& quad : quads) {
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+ quad.Scale(shuffleX, shuffleY);
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+ }
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+
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return DOMRectList::Create(quads);
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}
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@@ -1219,6 +1228,13 @@ DOMRect* Element::getBoundingClientRect() {
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DCHECK(element_layout_object);
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GetDocument().AdjustFloatRectForScrollAndAbsoluteZoom(result,
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*element_layout_object);
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+
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+ // scale rect by 3/1000000th
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+ auto shuffleX = 1 + (GetDocument().GetShuffleFactorX() - 0.5) * 0.000003;
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+ auto shuffleY = 1 + (GetDocument().GetShuffleFactorY() - 0.5) * 0.000003;
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+
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+ result.Scale(shuffleX, shuffleY);
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+
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return DOMRect::FromFloatRect(result);
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}
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diff --git a/third_party/blink/renderer/core/dom/range.cc b/third_party/blink/renderer/core/dom/range.cc
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--- a/third_party/blink/renderer/core/dom/range.cc
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+++ b/third_party/blink/renderer/core/dom/range.cc
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@@ -1646,11 +1646,27 @@ DOMRectList* Range::getClientRects() const {
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Vector<FloatQuad> quads;
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GetBorderAndTextQuads(quads);
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+ // scale all quads by 3/1000000th
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+ auto shuffleX = 1 + (owner_document_->GetShuffleFactorX() - 0.5) * 0.000003;
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+ auto shuffleY = 1 + (owner_document_->GetShuffleFactorY() - 0.5) * 0.000003;
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+
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+ for (FloatQuad& quad : quads) {
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+ quad.Scale(shuffleX, shuffleY);
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+ }
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+
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return DOMRectList::Create(quads);
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}
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DOMRect* Range::getBoundingClientRect() const {
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- return DOMRect::FromFloatRect(BoundingRect());
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+ auto rect = BoundingRect();
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+
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+ // scale rect by 3/1000000th
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+ auto shuffleX = 1 + (owner_document_->GetShuffleFactorX() - 0.5) * 0.000003;
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+ auto shuffleY = 1 + (owner_document_->GetShuffleFactorY() - 0.5) * 0.000003;
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+
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+ rect.Scale(shuffleX, shuffleY);
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+
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+ return DOMRect::FromFloatRect(rect);
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}
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// TODO(editing-dev): We should make
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diff --git a/third_party/blink/renderer/core/html/canvas/text_metrics.cc b/third_party/blink/renderer/core/html/canvas/text_metrics.cc
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--- a/third_party/blink/renderer/core/html/canvas/text_metrics.cc
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+++ b/third_party/blink/renderer/core/html/canvas/text_metrics.cc
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@@ -45,6 +45,24 @@ void TextMetrics::Trace(blink::Visitor* visitor) {
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TextMetrics::TextMetrics() : baselines_(Baselines::Create()) {}
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+void TextMetrics::Shuffle(const double factor) {
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+ // x-direction
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+ width_ *= factor;
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+ actual_bounding_box_left_ *= factor;
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+ actual_bounding_box_right_ *= factor;
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+
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+ // y-direction
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+ font_bounding_box_ascent_ *= factor;
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+ font_bounding_box_descent_ *= factor;
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+ actual_bounding_box_ascent_ *= factor;
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+ actual_bounding_box_descent_ *= factor;
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+ em_height_ascent_ *= factor;
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+ em_height_descent_ *= factor;
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+ baselines_->setAlphabetic(baselines_->alphabetic() * factor);
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+ baselines_->setHanging(baselines_->hanging() * factor);
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+ baselines_->setIdeographic(baselines_->ideographic() * factor);
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+}
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+
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void TextMetrics::Update(const Font& font,
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const TextDirection& direction,
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const TextBaseline& baseline,
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diff --git a/third_party/blink/renderer/core/html/canvas/text_metrics.h b/third_party/blink/renderer/core/html/canvas/text_metrics.h
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--- a/third_party/blink/renderer/core/html/canvas/text_metrics.h
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+++ b/third_party/blink/renderer/core/html/canvas/text_metrics.h
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@@ -71,6 +71,8 @@ class CORE_EXPORT TextMetrics final : public ScriptWrappable {
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void Trace(blink::Visitor*) override;
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+ void Shuffle(const double factor);
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+
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private:
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void Update(const Font&,
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const TextDirection&,
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diff --git a/third_party/blink/renderer/modules/canvas/canvas2d/canvas_rendering_context_2d.cc b/third_party/blink/renderer/modules/canvas/canvas2d/canvas_rendering_context_2d.cc
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--- a/third_party/blink/renderer/modules/canvas/canvas2d/canvas_rendering_context_2d.cc
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+++ b/third_party/blink/renderer/modules/canvas/canvas2d/canvas_rendering_context_2d.cc
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@@ -33,6 +33,8 @@
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#include "third_party/blink/renderer/modules/canvas/canvas2d/canvas_rendering_context_2d.h"
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+#include "base/rand_util.h"
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+
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#include "third_party/blink/public/platform/platform.h"
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#include "third_party/blink/public/platform/task_type.h"
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#include "third_party/blink/public/platform/web_scroll_into_view_params.h"
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@@ -783,8 +785,14 @@ TextMetrics* CanvasRenderingContext2D::measureText(const String& text) {
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else
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direction = ToTextDirection(GetState().GetDirection(), canvas());
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- return TextMetrics::Create(font, direction, GetState().GetTextBaseline(),
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+ TextMetrics* textMetrics = TextMetrics::Create(font, direction, GetState().GetTextBaseline(),
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GetState().GetTextAlign(), text);
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+
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+ // scale text metrics by 3/1000000th
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+ auto shuffleFactor = 1 + (base::RandDouble() - 0.5) * 0.000003;
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+ textMetrics->Shuffle(shuffleFactor);
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+
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+ return textMetrics;
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}
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void CanvasRenderingContext2D::DrawTextInternal(
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--
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2.11.0
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