Use SaveLayerAlpha bounds when doing Save-Draw-Restore optimization

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

 // Copyright 2016 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/PaintGeneratedImage.h"
 
 #include "platform/geometry/FloatRect.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/paint/PaintRecord.h"
 
 namespace blink {
 
 void PaintGeneratedImage::Draw(PaintCanvas* canvas,
                                const PaintFlags& flags,
                                const FloatRect& dest_rect,
                                const FloatRect& src_rect,
                                RespectImageOrientationEnum,
                                ImageClampingMode) {
   PaintCanvasAutoRestore ar(canvas, true);
   canvas->clipRect(dest_rect);
   canvas->translate(dest_rect.X(), dest_rect.Y());
   if (dest_rect.Size() != src_rect.Size())
     canvas->scale(dest_rect.Width() / src_rect.Width(),
                   dest_rect.Height() / src_rect.Height());
   canvas->translate(-src_rect.X(), -src_rect.Y());
-  SkRect bounds = dest_rect;
+  SkRect bounds = SkRect::MakeWH(src_rect.Width(), src_rect.Height());
   canvas->saveLayer(&bounds, &flags);
   canvas->drawPicture(record_);
 }
 
 void PaintGeneratedImage::DrawTile(GraphicsContext& context,
                                    const FloatRect& src_rect) {
   context.DrawRecord(record_);
 }
 
 }  // namespace blink