Collects stats on how user interacts with the bubble.

ui/views/bubble/bubble_frame_view.h

Index: ui/views/bubble/bubble_frame_view.h
diff --git a/ui/views/bubble/bubble_frame_view.h b/ui/views/bubble/bubble_frame_view.h
index a17a4f8f487eede0823a540e7654ceee3544b2cd..08dfc2cfca520309acedf50a4b0725de1fa74dba 100644
--- a/ui/views/bubble/bubble_frame_view.h
+++ b/ui/views/bubble/bubble_frame_view.h
@@ -6,6 +6,7 @@
 #define UI_VIEWS_BUBBLE_BUBBLE_FRAME_VIEW_H_
 
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/gtest_prod_util.h"
 #include "ui/gfx/insets.h"
@@ -79,6 +80,10 @@ class VIEWS_EXPORT BubbleFrameView : public NonClientFrameView,
                                    gfx::Size client_size,
                                    bool adjust_if_offscreen);
 
+  void set_before_close_callback(base::Closure c) {
+    before_close_callback_ = c;
+  }
+
  protected:
   // Returns the available screen bounds if the frame were to show in |rect|.
   virtual gfx::Rect GetAvailableScreenBounds(const gfx::Rect& rect);
@@ -114,6 +119,10 @@ class VIEWS_EXPORT BubbleFrameView : public NonClientFrameView,
   // (x) close button.
   View* titlebar_extra_view_;
 
+  // The callback function is executed before bubble is closed. It can be used
+  // to customize bubble's close behavior.
+  base::Closure before_close_callback_;
+
   DISALLOW_COPY_AND_ASSIGN(BubbleFrameView);
 };