Paint: remove readPixels.

ui/gfx/canvas.cc

 // Copyright (c) 2012 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 "ui/gfx/canvas.h"
 
 #include <cmath>
 #include <limits>
 
 #include "base/i18n/rtl.h"
@@ skipping 86 matching lines @@
   SizeStringFloat(text, font_list, &width, &height, 0, NO_ELLIPSIS);
   return width;
 }
 
 // static
 int Canvas::DefaultCanvasTextAlignment() {
   return base::i18n::IsRTL() ? TEXT_ALIGN_RIGHT : TEXT_ALIGN_LEFT;
 }
 
 ImageSkiaRep Canvas::ExtractImageRep() const {
-  // Make a bitmap to return, and a canvas to draw into it. We don't just want
-  // to call extractSubset or the copy constructor, since we want an actual copy
-  // of the bitmap.
-  const SkISize size = canvas_->getBaseLayerSize();
-  SkBitmap result;
-  result.allocN32Pixels(size.width(), size.height());
-
-  canvas_->readPixels(&result, 0, 0);
-  return ImageSkiaRep(result, image_scale_);
+  DCHECK(bitmap_);
+  SkBitmap bitmap_copy;
+  // |copyTo| will perform a deep copy, which is what we want.

[sky, 2017/04/05 03:00:24]

Generally we use |s for references to variables and parameters, and () for
references to functions, e.g. copyTo() here.

[vmpstr, 2017/04/05 19:13:39]

Done.

+  bool result = bitmap_->copyTo(&bitmap_copy);
+  DCHECK(result);

[sky, 2017/04/05 03:00:24]

Document why result should be true here.

[vmpstr, 2017/04/05 19:13:39]

Done.

+  return ImageSkiaRep(bitmap_copy, image_scale_);
 }
 
 void Canvas::DrawDashedRect(const Rect& rect, SkColor color) {
   DrawDashedRect(RectF(rect), color);
 }
 
 void Canvas::DrawDashedRect(const RectF& rect, SkColor color) {
   if (rect.IsEmpty())
     return;
   // Create a 2D bitmap containing alternating on/off pixels - we do this
@@ skipping 488 matching lines @@
   bitmap_.emplace();
   bitmap_->allocPixels(info);
   // Ensure that the bitmap is zeroed, since the code expects that.
   memset(bitmap_->getPixels(), 0, bitmap_->getSafeSize());
 
   owned_canvas_ = cc::SkiaPaintCanvas(bitmap_.value());
   return &owned_canvas_.value();
 }
 
 }  // namespace gfx