Disable GPU acceleration on 2D canvas when readbacks are needed

third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
index 3d4ef0a1a3c796c9c8924e38c78b2339033c701f..e5b4a2b4db5de78fa9b5dd1cbcd68d44fd68f5bd 100644
--- a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
@@ -1290,6 +1290,12 @@ PassRefPtr<Image> HTMLCanvasElement::getSourceImageForCanvas(
                   ? buffer()->newSkImageSnapshot(hint, reason)
                   : createTransparentImage(size())->imageForCurrentFrame();
   } else {
+    if (ExpensiveCanvasHeuristicParameters::
+            DisableAccelerationToAvoidReadbacks &&
+        !RuntimeEnabledFeatures::canvas2dFixedRenderingModeEnabled() &&
+        hint == PreferNoAcceleration && m_context->isAccelerated() &&
+        hasImageBuffer())
+      buffer()->disableAcceleration();
     RefPtr<blink::Image> image = renderingContext()->getImage(hint, reason);
     skImage = image ? image->imageForCurrentFrame()
                     : createTransparentImage(size())->imageForCurrentFrame();