Transparent apps support

chrome/browser/ui/views/extensions/native_app_window_views.cc

Index: chrome/browser/ui/views/extensions/native_app_window_views.cc
diff --git a/chrome/browser/ui/views/extensions/native_app_window_views.cc b/chrome/browser/ui/views/extensions/native_app_window_views.cc
index e84b7ac0321ffe19ba6e04e0eb563507d3576d9b..4a066f60ddd913d0c695dc34408558d3bd7eff6b 100644
--- a/chrome/browser/ui/views/extensions/native_app_window_views.cc
+++ b/chrome/browser/ui/views/extensions/native_app_window_views.cc
@@ -46,7 +46,9 @@ NativeAppWindowViews::NativeAppWindowViews(
       web_view_(NULL),
       window_(NULL),
       is_fullscreen_(false),
-      frameless_(create_params.frame == ShellWindow::FRAME_NONE) {
+      frameless_(create_params.frame == ShellWindow::FRAME_NONE),
+      transparent_background_(create_params.transparent_background) {
+  Observe(shell_window_->web_contents());
   minimum_size_ = create_params.minimum_size;
   maximum_size_ = create_params.maximum_size;
 
@@ -391,6 +393,23 @@ void NativeAppWindowViews::OnWidgetActivationChanged(views::Widget* widget,
   shell_window_->OnNativeWindowChanged();
 }
 
+// WebContentsObserver implementation.
+
+void NativeAppWindowViews::RenderViewCreated(
+    content::RenderViewHost* render_view_host) {
+  if (transparent_background_) {
+    // Use a background with transparency to trigger transparency in Webkit.
+    SkBitmap background;
+    background.setConfig(SkBitmap::kARGB_8888_Config, 1, 1);
+    background.allocPixels();
+    background.eraseARGB(0x00, 0x00, 0x00, 0x00);
+
+    content::RenderWidgetHostView* view = render_view_host->GetView();
+    DCHECK(view);
+    view->SetBackground(background);
+  }
+}
+
 // views::View implementation.
 
 void NativeAppWindowViews::Layout() {