Not disable acceleration in getImage if its Desynchronized

This is a temporary fix for this issue, that will totally be fixed
after we land the new 2d canvas api (that will completely remove the
path of code causing this regression in base_rendering_context_2d.cc:
  if (!RuntimeEnabledFeatures::NewCanvas2DAPIEnabled()) {
    // GetImagedata is faster in Unaccelerated canvases
    // Do not disaccelerate if Desync2d Canvas on android.
    // Issue 1112060: putImageData() does not work for desynchronized 2D canvas
    // on Android
    if (IsAccelerated()) {
      DisableAcceleration();
      base::UmaHistogramEnumeration("Blink.Canvas.GPUFallbackToCPU",
                                    GPUFallbackToCPUScenario::kGetImageData);
    }
  }

This CL specifically disables that path if the canvas is Desynchronized.
To do so this CL adds some infrastructural elements to be able to access
to the desynchronization setting inside getImage.

This issue is only happening in a very specific corner case, which
proves hard to be tested. This code will be deleted once we enable
the new canvas api - so this is a temporary fix.

Bug: 1112060
Change-Id: I60b90f716332b3969c82dfef3431e4cbd66e6500
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2541063Reviewed-by: Aaron Krajeski <aaronhk@chromium.org>
Commit-Queue: Juanmi Huertas <juanmihd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#829679}

third_party/blink/renderer/modules/canvas/canvas2d/base_rendering_context_2d.cc

@@ -1696,12 +1696,14 @@ ImageData* BaseRenderingContext2D::getImageDataInternal(
 
   // TODO(crbug.com/1101055): Remove the check for NewCanvas2DAPI flag once
   // released.
-  // New Canvas2D API utilizes willReadFrequently attribute that let the users
-  // indicate if a canvas will be read frequently through getImageData, thus
-  // uses CPU rendering from the start in such cases. (crbug.com/1090180)
+  // TODO(crbug.com/1090180): New Canvas2D API utilizes willReadFrequently
+  // attribute that let the users indicate if a canvas will be read frequently
+  // through getImageData, thus uses CPU rendering from the start in such cases.
   if (!RuntimeEnabledFeatures::NewCanvas2DAPIEnabled()) {
-    // GetImagedata is faster in Unaccelerated canvases
-    if (IsAccelerated()) {
+    // GetImagedata is faster in Unaccelerated canvases.
+    // In Desynchronized canvas disabling the acceleration will break
+    // putImageData: crbug.com/1112060.
+    if (IsAccelerated() && !IsDesynchronized()) {
       DisableAcceleration();
       base::UmaHistogramEnumeration("Blink.Canvas.GPUFallbackToCPU",
                                     GPUFallbackToCPUScenario::kGetImageData);

third_party/blink/renderer/modules/canvas/canvas2d/base_rendering_context_2d.h

@@ -253,6 +253,11 @@ class MODULES_EXPORT BaseRenderingContext2D : public GarbageCollectedMixin,
 
   virtual bool HasAlpha() const = 0;
 
+  virtual bool IsDesynchronized() const {
+    NOTREACHED();
+    return false;
+  }
+
   virtual bool isContextLost() const = 0;
 
   virtual void WillDrawImage(CanvasImageSource*) const {}

third_party/blink/renderer/modules/canvas/canvas2d/canvas_rendering_context_2d.h

@@ -278,6 +278,9 @@ class MODULES_EXPORT CanvasRenderingContext2D final
   bool IsAccelerated() const override;
   bool IsOriginTopLeft() const override;
   bool HasAlpha() const override { return CreationAttributes().alpha; }
+  bool IsDesynchronized() const override {
+    return CreationAttributes().desynchronized;
+  }
   void SetIsInHiddenPage(bool) override;
   void SetIsBeingDisplayed(bool) override;
   void Stop() final;

third_party/blink/renderer/modules/canvas/offscreencanvas2d/offscreen_canvas_rendering_context_2d.h

@@ -122,6 +122,9 @@ class MODULES_EXPORT OffscreenCanvasRenderingContext2D final
   void ValidateStateStackWithCanvas(const cc::PaintCanvas*) const final;
 
   bool HasAlpha() const final { return CreationAttributes().alpha; }
+  bool IsDesynchronized() const final {
+    return CreationAttributes().desynchronized;
+  }
   bool isContextLost() const override;
 
   ImageBitmap* TransferToImageBitmap(ScriptState*) final;