Usage graphs support RTL style.

Flips the canvas horizontally before drawing paths under RTL mode.

Bug: 78008951
Test: manually verified graphs of wifi data usage, app data usage, and
battery usage.

Change-Id: I79286e9f3f98632e3a9710d42c3e197231a14c39

res/layout/usage_view.xml

@@ -80,8 +80,7 @@
             android:layout_width="0dp"
             android:layout_height="wrap_content"
             android:layout_weight="1"
-            android:orientation="horizontal"
-            android:layoutDirection="ltr">
+            android:orientation="horizontal">
             <include android:id="@+id/label_start"
                      layout="@layout/usage_side_label" />
 

src/com/android/settings/widget/UsageGraph.java

@@ -255,9 +255,15 @@ public class UsageGraph extends View {
             return;
         }
 
+        canvas.save();
+        if (getLayoutDirection() == LAYOUT_DIRECTION_RTL) {
+            // Flip the canvas along the y-axis of the center of itself before drawing paths.
+            canvas.scale(-1, 1, canvas.getWidth() * 0.5f, 0);
+        }
         drawLinePath(canvas, mLocalProjectedPaths, mDottedPaint);
         drawFilledPath(canvas, mLocalPaths, mFillPaint);
         drawLinePath(canvas, mLocalPaths, mLinePaint);
+        canvas.restore();
         BatteryUtils.logRuntime(LOG_TAG, "onDraw", startTime);
     }