chromeos: Run beforeunload handlers when closing panels.

chrome/browser/chromeos/frame/panel_controller.h

Index: chrome/browser/chromeos/frame/panel_controller.h
diff --git a/chrome/browser/chromeos/frame/panel_controller.h b/chrome/browser/chromeos/frame/panel_controller.h
index e642cfe78188a3f6193a289352e74066a8677c1a..2d039bc35eff9f54ef4aac6d61c7957a8d27836f 100644
--- a/chrome/browser/chromeos/frame/panel_controller.h
+++ b/chrome/browser/chromeos/frame/panel_controller.h
@@ -44,6 +44,10 @@ class PanelController {
     // Retrieves the icon to use in the panel's titlebar.
     virtual SkBitmap GetPanelIcon() = 0;
 
+    // Can the panel be closed?  Called before ClosePanel() when the close
+    // button is pressed to give beforeunload handlers a chance to cancel.
+    virtual bool CanClosePanel() = 0;
+
     // Close the panel. Called when a close button is pressed.
     virtual void ClosePanel() = 0;
   };