Disables EnableAccelerationToAvoidReadbacks due to regression

third_party/WebKit/Source/platform/graphics/ExpensiveCanvasHeuristicParameters.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ExpensiveCanvasHeuristicParameters_h
 #define ExpensiveCanvasHeuristicParameters_h
 
 namespace blink {
 
 namespace ExpensiveCanvasHeuristicParameters {
@@ skipping 76 matching lines @@
   // prevent future canvas-to-canvas draws from requiring a readback.
   DisableAccelerationToAvoidReadbacks = 0,
 
   // See description of DisableAccelerationToAvoidReadbacks. This is the
   // opposite strategy : accelerate the destination canvas. If both
   // EnableAccelerationToAvoidReadbacks and
   // DisableAccelerationToAvoidReadbacks are specified, we try to enable
   // acceleration on the destination first. If that does not succeed,
   // we disable acceleration on the source canvas. Either way, future
   // readbacks are prevented.
-  EnableAccelerationToAvoidReadbacks = 1,
+  EnableAccelerationToAvoidReadbacks = 0,
 
 };  // enum
 
 // Constants and Coefficients for 2D Canvas Dynamic Rendering Mode Switching
 // =========================================================================
 
 // Approximate relative costs of different types of operations for the
 // accelerated rendering pipeline and the recording rendering pipeline.
 // These costs were estimated experimentally using the tools located in the
 // third_party/WebKit/Source/modules/canvas2d/performance_analysis directory.
@@ skipping 94 matching lines @@
 // before the rendering pipeline may be switched. Having this set
 // to more than 1 increases the sample size of usage data before a
 // decision is made, improving the accuracy of heuristics.
 const int MinFramesBeforeSwitch = 3;
 
 }  // namespace ExpensiveCanvasHeuristicParameters
 
 }  // namespace blink
 
 #endif