Improved heuristic for disable acceleration.

third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.h

Index: third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.h
diff --git a/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.h b/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.h
index 10dab808eb768aa56acb2e5273836a1a5ea4dd48..0441cecc4d5467c08fd3a337d049cc6ccca3810b 100644
--- a/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.h
+++ b/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.h
@@ -35,6 +35,7 @@
 #include "modules/canvas2d/BaseRenderingContext2D.h"
 #include "modules/canvas2d/Canvas2DContextAttributes.h"
 #include "modules/canvas2d/CanvasRenderingContext2DState.h"
+#include "platform/graphics/ExpensiveCanvasHeuristicParameters.h"
 #include "platform/graphics/GraphicsTypes.h"
 #include "platform/heap/GarbageCollected.h"
 #include "public/platform/WebThread.h"
@@ -224,6 +225,8 @@ private:
     HashMap<String, Font> m_fontsResolvedUsingCurrentStyle;
     bool m_pruneLocalFontCacheScheduled;
     ListHashSet<String> m_fontLRUList;
+
+    double estimateRenderingCostForUsage(BaseRenderingContext2D::UsageCounters, ExpensiveCanvasHeuristicParameters::RenderingModeCostIndex) const;

[Justin Novosad, 2016/08/04 15:53:17]

Why does UsageCounters need to be an argument? getUsage() is accessible from
this method.
The "ForUsage" part of the name does not add useful information.
This estimation method belongs in BaseRenderingContext2D IMHO, so that we'll be
able to use it for OffscreenCanvases.

[sebastienlc, 2016/08/04 16:36:27]

Done.

 };
 
 DEFINE_TYPE_CASTS(CanvasRenderingContext2D, CanvasRenderingContext, context, context->is2d(), context.is2d());