[Aura] Support transparent webkit.

content/browser/renderer_host/backing_store_skia.cc

 // Copyright (c) 2011 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 "content/browser/renderer_host/backing_store_skia.h"
 
 #include "content/browser/renderer_host/render_process_host.h"
 #include "skia/ext/platform_canvas.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/canvas_skia.h"
 #include "ui/gfx/rect.h"
 
 // Assume that somewhere along the line, someone will do width * height * 4
 // with signed numbers. If the maximum value is 2**31, then 2**31 / 4 =
 // 2**29 and floor(sqrt(2**29)) = 23170.
 
 // Max height and width for layers
 static const int kMaxVideoLayerSize = 23170;
 
 BackingStoreSkia::BackingStoreSkia(RenderWidgetHost* widget,
                                    const gfx::Size& size)
     : BackingStore(widget, size) {
   bitmap_.setConfig(SkBitmap::kARGB_8888_Config, size.width(), size.height());
   bitmap_.allocPixels();
   canvas_.reset(new SkCanvas(bitmap_));
+  copy_paint_.setXfermodeMode(SkXfermode::kSrc_Mode);
 }
 
 BackingStoreSkia::~BackingStoreSkia() {
 }
 
 void BackingStoreSkia::SkiaShowRect(const gfx::Point& point,
                                     gfx::Canvas* canvas) {
   canvas->GetSkCanvas()->drawBitmap(bitmap_,
       SkIntToScalar(point.x()), SkIntToScalar(point.y()));
 }
@@ skipping 29 matching lines @@
   for (size_t i = 0; i < copy_rects.size(); i++) {
     const gfx::Rect& copy_rect = copy_rects[i];
     int x = copy_rect.x() - bitmap_rect.x();
     int y = copy_rect.y() - bitmap_rect.y();
     int w = copy_rect.width();
     int h = copy_rect.height();
     SkIRect srcrect = SkIRect::MakeXYWH(x, y, w, h);
     SkRect dstrect = SkRect::MakeXYWH(
         SkIntToScalar(copy_rect.x()), SkIntToScalar(copy_rect.y()),
         SkIntToScalar(w), SkIntToScalar(h));
-    canvas_.get()->drawBitmapRect(sk_bitmap, &srcrect, dstrect);
+    canvas_.get()->drawBitmapRect(sk_bitmap, &srcrect, dstrect, &copy_paint_);

[brettw, 2011/10/21 20:14:44]

In other places we haven't bothered saving the SkPaint. I'd probably just create
it on the stack when you need it, unless you have a strong reason to do it like
this.

[xiyuan, 2011/10/21 20:24:05]

Done.

   }
 }
 
 void BackingStoreSkia::ScrollBackingStore(int dx, int dy,
                                           const gfx::Rect& clip_rect,
                                           const gfx::Size& view_size) {
   int x = std::min(clip_rect.x(), clip_rect.x() - dx);
   int y = std::min(clip_rect.y(), clip_rect.y() - dy);
   int w = clip_rect.width() + abs(dx);
   int h = clip_rect.height() + abs(dy);
   SkIRect rect = SkIRect::MakeXYWH(x, y, w, h);
   bitmap_.scrollRect(&rect, dx, dy);
 }
 
 bool BackingStoreSkia::CopyFromBackingStore(const gfx::Rect& rect,
                                             skia::PlatformCanvas* output) {
   const int width = std::min(size().width(), rect.width());
   const int height = std::min(size().height(), rect.height());
   if (!output->initialize(width, height, true))
     return false;
 
   SkBitmap bitmap = skia::GetTopDevice(*output)->accessBitmap(true);
   SkIRect skrect = SkIRect::MakeXYWH(rect.x(), rect.y(), width, height);
   SkBitmap b;
   if (!canvas_->readPixels(skrect, &b))
     return false;
   output->writePixels(b, rect.x(), rect.y());
   return true;
 }