Expose if we are using swiftshader via WebGraphicsContext3DProvider.

third_party/WebKit/public/platform/Platform.h

 /*
  * Copyright (C) 2012 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 443 matching lines @@
         WebGraphicsContext3DProvider* shareContext,
         GraphicsInfo*) { return nullptr; }
 
     // Returns a newly allocated and initialized offscreen context provider,
     // backed by the process-wide shared main thread context. Returns null if
     // the context cannot be created or initialized.
     virtual WebGraphicsContext3DProvider* createSharedOffscreenGraphicsContext3DProvider() { return nullptr; }
 
     virtual std::unique_ptr<cc::SharedBitmap> allocateSharedBitmap(const WebSize& size) { return nullptr; }
 
-    // Returns true if the platform is capable of producing an offscreen context suitable for accelerating 2d canvas.
-    // This will return false if the platform cannot promise that contexts will be preserved across operations like
-    // locking the screen or if the platform cannot provide a context with suitable performance characteristics.
-    //
-    // This value must be checked again after a context loss event as the platform's capabilities may have changed.
-    virtual bool canAccelerate2dCanvas() { return false; }
-
     virtual bool isThreadedCompositingEnabled() { return false; }
     virtual bool isThreadedAnimationEnabled() { return true; }
 
     virtual WebCompositorSupport* compositorSupport() { return nullptr; }
 
     virtual WebFlingAnimator* createFlingAnimator() { return nullptr; }
 
     // Creates a new fling animation curve instance for device |deviceSource|
     // with |velocity| and already scrolled |cumulativeScroll| pixels.
     virtual WebGestureCurve* createFlingAnimationCurve(WebGestureDevice deviceSource, const WebFloatPoint& velocity, const WebSize& cumulativeScroll) { return nullptr; }
@@ skipping 115 matching lines @@
 protected:
     Platform();
     virtual ~Platform() { }
 
     WebThread* m_mainThread;
 };
 
 } // namespace blink
 
 #endif