Transparent apps support

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

Index: chrome/browser/ui/views/extensions/shell_window_views.cc
diff --git a/chrome/browser/ui/views/extensions/shell_window_views.cc b/chrome/browser/ui/views/extensions/shell_window_views.cc
index 02199e94fabc0bbf46634c90493fd009ce41036c..970d99705a66cc8426f26e435c5eb9940f8a8e1b 100644
--- a/chrome/browser/ui/views/extensions/shell_window_views.cc
+++ b/chrome/browser/ui/views/extensions/shell_window_views.cc
@@ -319,7 +319,9 @@ ShellWindowViews::ShellWindowViews(ShellWindow* shell_window,
     : shell_window_(shell_window),
       web_view_(NULL),
       is_fullscreen_(false),
-      frameless_(win_params.frame == ShellWindow::CreateParams::FRAME_NONE) {
+      frameless_(win_params.frame == ShellWindow::CreateParams::FRAME_NONE),
+      transparent_background_(win_params.transparent_background) {
+  Observe(shell_window_->web_contents());
   window_ = new views::Widget;
   views::Widget::InitParams params(views::Widget::InitParams::TYPE_WINDOW);
   params.delegate = this;
@@ -605,6 +607,21 @@ bool ShellWindowViews::ShouldShowWindowTitle() const {
   return false;
 }
 
+void ShellWindowViews::RenderViewCreated(
+    content::RenderViewHost* render_view_host) {
+  if (transparent_background_) {

[sky, 2012/09/28 22:29:13]

Does this result in flicker? Might it be possible for the page to attempt to
paint before this is applied?

[Bernie, 2012/10/10 21:05:01]

The window opens with a white background, then it becomes transparent, and the
content is rendered last.

I'm not sure where we could hook to make the background transparent earlier than
this.

[reveman, 2012/10/11 17:25:58]

We'll need to fix this. But I think it's OK to address it in a follow up patch
if you just file a bug for it and reference that bug in a TODO comment here.

+    // 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);
+  }
+}
+
 void ShellWindowViews::Layout() {
   DCHECK(web_view_);
   web_view_->SetBounds(0, 0, width(), height());