Refactor CRC2D::reset() to avoid non-additive SkCanvas state operations

third_party/WebKit/Source/platform/graphics/RecordingImageBufferSurface.cpp

 // Copyright 2014 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.
 
 #include "platform/graphics/RecordingImageBufferSurface.h"
 
 #include "platform/Histogram.h"
 #include "platform/graphics/CanvasMetrics.h"
 #include "platform/graphics/ExpensiveCanvasHeuristicParameters.h"
 #include "platform/graphics/GraphicsContext.h"
@@ skipping 21 matching lines @@
       m_previousFrameHasExpensiveOp(false),
       m_fallbackFactory(std::move(fallbackFactory)) {
   initializeCurrentFrame();
 }
 
 RecordingImageBufferSurface::~RecordingImageBufferSurface() {}
 
 void RecordingImageBufferSurface::initializeCurrentFrame() {
   static SkRTreeFactory rTreeFactory;
   m_currentFrame = wrapUnique(new SkPictureRecorder);
-  m_currentFrame->beginRecording(size().width(), size().height(),
-                                 &rTreeFactory);
+  SkCanvas* canvas = m_currentFrame->beginRecording(
+      size().width(), size().height(), &rTreeFactory);
+  // Always save an initial frame, to support resetting the top level matrix
+  // and clip.
+  canvas->save();
+
   if (m_imageBuffer) {
-    m_imageBuffer->resetCanvas(m_currentFrame->getRecordingCanvas());
+    m_imageBuffer->resetCanvas(canvas);
   }
   m_didRecordDrawCommandsInCurrentFrame = false;
   m_currentFrameHasExpensiveOp = false;
   m_currentFramePixelCount = 0;
 }
 
 void RecordingImageBufferSurface::setImageBuffer(ImageBuffer* imageBuffer) {
   m_imageBuffer = imageBuffer;
   if (m_currentFrame && m_imageBuffer) {
     m_imageBuffer->resetCanvas(m_currentFrame->getRecordingCanvas());
@@ skipping 233 matching lines @@
     CHECK(m_currentFrame);
     return true;
   }
 
   if (!m_frameWasCleared) {
     *fallbackReason = FallbackReasonCanvasNotClearedBetweenFrames;
     return false;
   }
 
   if (m_fallbackFactory &&
-      m_currentFrame->getRecordingCanvas()->getSaveCount() >
+      m_currentFrame->getRecordingCanvas()->getSaveCount() - 1 >
           ExpensiveCanvasHeuristicParameters::ExpensiveRecordingStackDepth) {
+    // (getSaveCount() decremented to account  for the intial recording canvas
+    // save frame.)
     *fallbackReason = FallbackReasonRunawayStateStack;
     return false;
   }
 
   m_previousFrame = m_currentFrame->finishRecordingAsPicture();
   m_previousFrameHasExpensiveOp = m_currentFrameHasExpensiveOp;
   m_previousFramePixelCount = m_currentFramePixelCount;
   initializeCurrentFrame();
 
   m_frameWasCleared = false;
@@ skipping 68 matching lines @@
 }
 
 void RecordingImageBufferSurface::setIsHidden(bool hidden) {
   if (m_fallbackSurface)
     m_fallbackSurface->setIsHidden(hidden);
   else
     ImageBufferSurface::setIsHidden(hidden);
 }
 
 }  // namespace blink