Use SaveLayerAlpha bounds when doing Save-Draw-Restore optimization

cc/paint/paint_op_buffer.h

 // Copyright 2017 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 CC_PAINT_PAINT_OP_BUFFER_H_
 #define CC_PAINT_PAINT_OP_BUFFER_H_
 
 #include <stdint.h>
 
 #include "base/logging.h"
@@ skipping 68 matching lines @@
   PaintOpType GetType() const { return static_cast<PaintOpType>(type); }
 
   // Subclasses should provide a static Raster() method which is called from
   // here. The Raster method should take a const PaintOp* parameter. It is
   // static with a pointer to the base type so that we can use it as a function
   // pointer.
   void Raster(SkCanvas* canvas, const SkMatrix& original_ctm) const;
   bool IsDrawOp() const;
 
   // Only valid for draw ops.
-  void RasterWithAlpha(SkCanvas* canvas, uint8_t alpha) const;
+  void RasterWithAlpha(SkCanvas* canvas,
+                       const SkRect& bounds,
+                       uint8_t alpha) const;
 
   int CountSlowPaths() const { return 0; }
   int CountSlowPathsFromFlags() const { return 0; }
 
   bool HasDiscardableImages() const { return false; }
   bool HasDiscardableImagesFromFlags() const { return false; }
 
   // Returns the number of bytes used by this op in referenced sub records
   // and display lists.  This doesn't count other objects like paths or blobs.
   size_t AdditionalBytesUsed() const { return 0; }
@@ skipping 869 matching lines @@
   // Record additional bytes used by referenced sub-records and display lists.
   size_t subrecord_bytes_used_ = 0;
   bool has_discardable_images_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(PaintOpBuffer);
 };
 
 }  // namespace cc
 
 #endif  // CC_PAINT_PAINT_OP_BUFFER_H_