Convert InfoBubble to using BubbleBorder. This also replaces the border grap...

chrome/browser/bubble_positioner.h

Index: chrome/browser/bubble_positioner.h
===================================================================
--- chrome/browser/bubble_positioner.h	(revision 26373)
+++ chrome/browser/bubble_positioner.h	(working copy)
@@ -10,12 +10,14 @@
 }
 
 // An object in the browser UI can implement this interface to provide display
-// bounds for the omnibox bubble.
+// bounds for the omnibox bubble and info bubble views.
 class BubblePositioner {
  public:
   // Returns the bounds of the "location bar" stack (including star/go buttons
   // where relevant).  The omnibox dropdown uses this to calculate its width and
-  // y-coordinate.
+  // y-coordinate, and views showing InfoBubbles use it to find the y-coordinate
+  // they should show at, so that all "bubble" UIs show up at the same vertical
+  // position.
   virtual gfx::Rect GetLocationStackBounds() const = 0;
 };