Reland: Make 2D canvas disable gpu acceleration when getImageData is called

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 44 matching lines @@
 
     // GPU vs. display list heuristic parameters
     //===========================================
 
     // Pixel count beyond which we should always prefer to use display
     // lists. Rationale: The allocation of large textures for canvas
     // tends to starve the compositor, and increase the probability of
     // failure of subsequent allocations required for double buffering.
     PreferDisplayListOverGpuSizeThreshold = 4096 * 4096,
 
+    // Disable Acceleration heuristic parameters
+    //===========================================
+
+    GetImageDataForcesNoAcceleration = 1,
+
 }; // enum
 
 } // namespace ExpensiveCanvasHeuristicParameters
 
 } // namespace blink
 
 #endif