Removing canvas rendering mode switching feature

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

Index: third_party/WebKit/Source/platform/graphics/ExpensiveCanvasHeuristicParameters.h
diff --git a/third_party/WebKit/Source/platform/graphics/ExpensiveCanvasHeuristicParameters.h b/third_party/WebKit/Source/platform/graphics/ExpensiveCanvasHeuristicParameters.h
deleted file mode 100644
index 18fea7254e8aa70a6b93bc884a47c21dee972c7d..0000000000000000000000000000000000000000
--- a/third_party/WebKit/Source/platform/graphics/ExpensiveCanvasHeuristicParameters.h
+++ /dev/null
@@ -1,216 +0,0 @@
-// 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 {
-
-enum {
-  // Layer promotion heuristic parameters
-  //======================================
-
-  // FIXME (crbug.com/463239):
-  // The Layer promotion heuristics should go away after slimming paint
-  // is completely phased in and display list canvases are modified to
-  // use a lightweight layering primitive instead of the
-  // SkCanvas::saveLayer.
-
-  // Heuristic: Canvases that are overdrawn beyond this factor in a
-  // single frame are promoted to a direct composited layer so that
-  // their contents not be re-rasterized by the compositor when the
-  // containing layer is the object of a paint invalidation.
-  kExpensiveOverdrawThreshold = 3,
-
-  kExpensivePathPointCount = 50,
-
-  kSVGImageSourcesAreExpensive = 1,
-
-  kConcavePathsAreExpensive = 1,
-
-  kComplexClipsAreExpensive = 1,
-
-  kBlurredShadowsAreExpensive = 1,
-
-  // Heuristic: When drawing a source image that has more pixels than
-  // the destination canvas by the following factor or more, the draw
-  // is considered expensive.
-  kExpensiveImageSizeRatio = 4,
-
-  // Display list fallback heuristic parameters
-  //============================================
-
-  // Frames ending with more than this number of levels remaining
-  // on the state stack at the end of a frame are too expensive to
-  // remain in display list mode. This criterion is motivated by an
-  // O(N) cost in carying over state from one frame to the next when
-  // in display list mode. The value of this parameter should be high
-  // enough to almost never kick in other than for cases with unmatched
-  // save()/restore() calls are low enough to kick in before state
-  // management becomes measurably expensive.
-  kExpensiveRecordingStackDepth = 50,
-
-  // 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.
-  kPreferDisplayListOverGpuSizeThreshold = 8096 * 4096,
-
-  // Disable Acceleration heuristic parameters
-  //===========================================
-
-  // When drawing very large images to canvases, there is a point where
-  // GPU acceleration becomes inefficient due to texture upload overhead,
-  // especially when the image is large enough that it is likely to
-  // monopolize the texture cache, and when it is being downsized to the
-  // point that few of the upload texels are actually sampled. When both
-  // of these conditions are met, we disable acceleration.
-  kDrawImageTextureUploadSoftSizeLimit = 4096 * 4096,
-  kDrawImageTextureUploadSoftSizeLimitScaleThreshold = 4,
-  kDrawImageTextureUploadHardSizeLimit = 8192 * 8192,
-
-  // GPU readback prevention heuristics
-  //====================================
-
-  kGPUReadbackForcesNoAcceleration = 1,
-
-  // When gpu readback is successively invoked in following number of frames,
-  // we disable gpu acceleration to avoid the high cost of gpu readback.
-  kGPUReadbackMinSuccessiveFrames = 3,
-
-  // When a canvas is used as a source image, if its destination is
-  // non-accelerated and the source canvas is accelerated, a readback
-  // from the gpu is necessary. This option causes the source canvas to
-  // switch to non-accelerated when this situation is encountered to
-  // prevent future canvas-to-canvas draws from requiring a readback.
-  kDisableAccelerationToAvoidReadbacks = 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.
-  kEnableAccelerationToAvoidReadbacks = 1,
-
-};  // 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.
-
-// The RenderingModeCostIndex enum is used to access the heuristic coefficients
-// that correspond to a given rendering mode. For example,
-// FillRectFixedCost[RecordingModeIndex] is the estimated fixed cost for
-// FillRect in recording mode.
-enum RenderingModeCostIndex {
-  kRecordingModeIndex = 0,
-  kAcceleratedModeIndex = 1,
-  kNumRenderingModesCostIndexes = 2
-};
-
-const float kFillRectFixedCost[kNumRenderingModesCostIndexes] = {6.190e-03f,
-                                                                 7.715e-03f};
-const float kFillConvexPathFixedCost[kNumRenderingModesCostIndexes] = {
-    1.251e-02f, 1.231e-02f};
-const float kFillNonConvexPathFixedCost[kNumRenderingModesCostIndexes] = {
-    1.714e-02f, 4.497e-02f};
-const float kFillTextFixedCost[kNumRenderingModesCostIndexes] = {1.119e-02f,
-                                                                 2.203e-02f};
-
-const float kStrokeRectFixedCost[kNumRenderingModesCostIndexes] = {1.485e-02f,
-                                                                   7.287e-03f};
-const float kStrokePathFixedCost[kNumRenderingModesCostIndexes] = {2.390e-02f,
-                                                                   5.125e-02f};
-const float kStrokeTextFixedCost[kNumRenderingModesCostIndexes] = {1.149e-02f,
-                                                                   1.742e-02f};
-
-const float kFillRectVariableCostPerArea[kNumRenderingModesCostIndexes] = {
-    2.933e-07f, 2.188e-09f};
-const float kFillConvexPathVariableCostPerArea[kNumRenderingModesCostIndexes] =
-    {7.871e-07f, 1.608e-07f};
-const float
-    kFillNonConvexPathVariableCostPerArea[kNumRenderingModesCostIndexes] = {
-        8.336e-07f, 1.384e-06f};
-const float kFillTextVariableCostPerArea[kNumRenderingModesCostIndexes] = {
-    1.411e-06f, 0.0f};
-
-const float kStrokeRectVariableCostPerArea[kNumRenderingModesCostIndexes] = {
-    9.882e-07f, 0.0f};
-const float kStrokePathVariableCostPerArea[kNumRenderingModesCostIndexes] = {
-    1.583e-06f, 2.401e-06f};
-const float kStrokeTextVariableCostPerArea[kNumRenderingModesCostIndexes] = {
-    1.530e-06f, 6.699e-07f};
-
-const float kPatternFillTypeFixedCost[kNumRenderingModesCostIndexes] = {
-    1.377e-02f, 1.035e-02f};
-const float kLinearGradientFillTypeFixedCost[kNumRenderingModesCostIndexes] = {
-    7.694e-03f, 6.900e-03f};
-const float kRadialGradientFillTypeFixedCost[kNumRenderingModesCostIndexes] = {
-    2.260e-02f, 7.193e-03f};
-
-const float kPatternFillTypeVariableCostPerArea[kNumRenderingModesCostIndexes] =
-    {6.080e-07f, 0.0f};
-const float
-    kLinearGradientFillVariableCostPerArea[kNumRenderingModesCostIndexes] = {
-        9.635e-07f, 0.0f};
-const float
-    kRadialGradientFillVariableCostPerArea[kNumRenderingModesCostIndexes] = {
-        6.662e-06f, 0.0f};
-
-const float kShadowFixedCost[kNumRenderingModesCostIndexes] = {2.502e-02f,
-                                                               2.274e-02f};
-const float kShadowVariableCostPerAreaTimesShadowBlurSquared
-    [kNumRenderingModesCostIndexes] = {6.856e-09f, 0.0f};
-
-const float kPutImageDataFixedCost[kNumRenderingModesCostIndexes] = {
-    1.209e-03f, 1.885e-02f};
-const float kPutImageDataVariableCostPerArea[kNumRenderingModesCostIndexes] = {
-    6.231e-06f, 4.116e-06f};
-
-const float kDrawSVGImageFixedCost[kNumRenderingModesCostIndexes] = {
-    1.431e-01f, 2.958e-01f};
-const float kDrawPNGImageFixedCost[kNumRenderingModesCostIndexes] = {
-    1.278e-02f, 1.306e-02f};
-
-const float kDrawSVGImageVariableCostPerArea[kNumRenderingModesCostIndexes] = {
-    1.030e-05f, 4.463e-06f};
-const float kDrawPNGImageVariableCostPerArea[kNumRenderingModesCostIndexes] = {
-    1.727e-06f, 0.0f};
-
-// Two conditions must be met before the isAccelerationOptimalForCanvasContent
-// heuristics recommends switching out of the accelerated mode:
-//   1. The difference in estimated cost per frame is larger than
-//      MinCostPerFrameImprovementToSuggestDisableAcceleration. This ensures
-//      that the overhead involved in a switch of rendering mode and the risk of
-//      making a wrong decision are justified by a large expected increased
-//      performance.
-//   2. The percent reduction in rendering cost is larger than
-//      MinPercentageImprovementToSuggestDisableAcceleration. This ensures that
-//      there is a high level of confidence that the performance would be
-//      improved in recording mode.
-const float kMinCostPerFrameImprovementToSuggestDisableAcceleration = 15.0f;
-const float kMinPercentageImprovementToSuggestDisableAcceleration = 30.0f;
-
-// Minimum number of frames that need to be rendered
-// 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 kMinFramesBeforeSwitch = 3;
-
-}  // namespace ExpensiveCanvasHeuristicParameters
-
-}  // namespace blink
-
-#endif