Protect keyboard geometry on Android

Prevent websites from inferring on-screen keyboard dimensions through
viewport changes, dynamic CSS viewport units, browser-controls geometry,
and the Virtual Keyboard API.

Keep Chromium content at its neutral pre-IME height inside a native
ProtectedViewportScrollView. Force overlays-content while protection is
active, expose an empty virtual-keyboard rectangle, and retain stable
browser-controls geometry throughout the IME transition.

Use the focused editable or caret bounds to pan the physical viewport
without resizing Blink. Preserve continuous scrolling by handing
unconsumed motion between the native ScrollView and cc while retaining
normal compositor hit testing for inner and root scrollers.

Add an enabled-by-default feature flag and a per-site content setting.
WebUI and extension pages retain Chromium's standard keyboard behavior.

build/cromite_patches_list.txt

@@ -310,6 +310,7 @@ Disable-AppRating.patch
 Enable-Android-DevTools-Frontend.patch
 Reduce-input-capability-fingerprinting-through-normalization.patch
 Disable-Android-HDR.patch
+Protect-keyboard-geometry-on-Android.patch
 
 # temporary or wip patches
 Temp-disable-predictive-back-gesture.patch