[Aura] Support transparent webkit.

Support turning on webkit transparency by setting a background image.
- Update RenderWidget::PaintRect to handle background transparency;
- Update BackingStoreSkia::PaintToBackingStore to handle webkit transparency;
- Turn on compositing of RenderWidgetHostViewAura's layer when we set a background with transparency;

BUG=98311
TEST=Verify when applist change (chromium:98308) is in.


Review URL: http://codereview.chromium.org/8369006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@106943 0039d316-1c4b-4281-b951-d872f2087c98

content/browser/renderer_host/backing_store_skia.cc

@@ -60,6 +60,9 @@ void BackingStoreSkia::PaintToBackingStore(
   if (!dib)
     return;
 
+  SkPaint copy_paint;
+  copy_paint.setXfermodeMode(SkXfermode::kSrc_Mode);
+
   SkBitmap sk_bitmap;
   sk_bitmap.setConfig(SkBitmap::kARGB_8888_Config, width, height);
   sk_bitmap.setPixels(dib->memory());
@@ -73,7 +76,7 @@ void BackingStoreSkia::PaintToBackingStore(
     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);
   }
 }
 

content/browser/renderer_host/render_widget_host_view_aura.cc

@@ -15,13 +15,13 @@
 #include "ui/aura/hit_test.h"
 #include "ui/aura/window.h"
 #include "ui/gfx/canvas.h"
+#include "ui/gfx/compositor/layer.h"
 
 #if defined(UI_COMPOSITOR_IMAGE_TRANSPORT)
 #include "base/bind.h"
 #include "content/browser/gpu/gpu_process_host_ui_shim.h"
 #include "content/browser/renderer_host/accelerated_surface_container_linux.h"
 #include "content/common/gpu/gpu_messages.h"
-#include "ui/gfx/compositor/layer.h"
 #include "ui/gfx/gl/gl_bindings.h"
 #endif
 
@@ -237,6 +237,7 @@ void RenderWidgetHostViewAura::AcceleratedSurfaceRelease(uint64 surface_id) {
 void RenderWidgetHostViewAura::SetBackground(const SkBitmap& background) {
   RenderWidgetHostView::SetBackground(background);
   host_->SetBackground(background);
+  window_->layer()->SetFillsBoundsOpaquely(background.isOpaque());
 }
 
 #if defined(OS_POSIX)

content/renderer/render_widget.cc

@@ -534,8 +534,19 @@ void RenderWidget::PaintRect(const gfx::Rect& rect,
                                                     SkShader::kRepeat_TileMode,
                                                     SkShader::kRepeat_TileMode);
     paint.setShader(shader)->unref();
-    paint.setXfermodeMode(SkXfermode::kSrcOver_Mode);
+
+    // Use kSrc_Mode to handle background_ transparency properly.
+    paint.setXfermodeMode(SkXfermode::kSrc_Mode);
+
+    // Canvas could contain multiple update rects. Clip to given rect so that
+    // we don't accidentally clear other update rects.
+    canvas->save();
+    SkRect clip;
+    clip.set(SkIntToScalar(rect.x()), SkIntToScalar(rect.y()),
+             SkIntToScalar(rect.right()), SkIntToScalar(rect.bottom()));
+    canvas->clipRect(clip);
     canvas->drawPaint(paint);
+    canvas->restore();
   }
 
   // First see if this rect is a plugin that can paint itself faster.