Improved heuristic for disable acceleration.

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

 /*
  * Copyright (C) 2006, 2007, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 17 matching lines @@
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/html/canvas/CanvasContextCreationAttributes.h"
 #include "core/html/canvas/CanvasRenderingContext.h"
 #include "core/html/canvas/CanvasRenderingContextFactory.h"
 #include "core/svg/SVGResourceClient.h"
 #include "modules/ModulesExport.h"
 #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"
 #include "wtf/Vector.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink { class WebLayer; }
 
 namespace blink {
 
@@ skipping 169 matching lines @@
     LostContextMode m_contextLostMode;
     bool m_contextRestorable;
     unsigned m_tryRestoreContextAttemptCount;
     Timer<CanvasRenderingContext2D> m_dispatchContextLostEventTimer;
     Timer<CanvasRenderingContext2D> m_dispatchContextRestoredEventTimer;
     Timer<CanvasRenderingContext2D> m_tryRestoreContextEventTimer;
 
     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());
 
 } // namespace blink
 
 #endif // CanvasRenderingContext2D_h