Always disable "content has shadow".

ui/base/cocoa/underlay_opengl_hosting_window.mm

Index: ui/base/cocoa/underlay_opengl_hosting_window.mm
diff --git a/ui/base/cocoa/underlay_opengl_hosting_window.mm b/ui/base/cocoa/underlay_opengl_hosting_window.mm
index e56323e22acd6fd23a45425544b74863f7df024a..e69c66fdda0409410b215433cd7b24d8c70b48f5 100644
--- a/ui/base/cocoa/underlay_opengl_hosting_window.mm
+++ b/ui/base/cocoa/underlay_opengl_hosting_window.mm
@@ -108,10 +108,17 @@ void RootDidAddSubview(id self, SEL _cmd, NSView* subview) {
     // all windows hosting OpenGL content must not be opaque.
     [self setOpaque:NO];
 
+    // Always disable "content has shadow". This class assumes that all holes
+    // punched in the window are intentional, in order to show accelerated
+    // content underneath, so those holes cannot be allowed to cause holes in
+    // the shadow. Note that the edges trimmed from around the periphery of a
+    // window (through use of transparency) don't count as content area with
+    // regards to "content has shadow".
+    [self _setContentHasShadow:NO];

[Nico, 2012/11/27 00:28:12]

Hum, I would've expected this to force a regulare rectangular window shadow for
the bubbles, instead of a shadow that follows the bubble shape. But if it looks
good on 10.6-10.8, lgtm

[Avi (use Gerrit), 2012/11/27 14:51:53]

That's the magic of "content has shadow = NO"; the shadow region is
scanline-by-scanline, first opaque pixel to last opaque pixel.

Or at least I hope so. I also need to verify on HiDPI too...

+
+    // Only set up opaques if the window is a proper window with a title bar
+    // and all.
     if (windowStyle & NSTitledWindowMask) {
-      // Only fiddle with shadows if the window is a proper window with a
-      // title bar and all.
-      [self _setContentHasShadow:NO];
 
       NSView* rootView = [[self contentView] superview];
       const NSRect rootBounds = [rootView bounds];