Add support for constrained windows on os x, based on Avi's GTMWindowSheetController.

chrome/browser/cocoa/browser_window_cocoa.h

Index: chrome/browser/cocoa/browser_window_cocoa.h
diff --git a/chrome/browser/cocoa/browser_window_cocoa.h b/chrome/browser/cocoa/browser_window_cocoa.h
index 688b6586a4f3ae725c67dac87b5e94fd9b087cf8..c93b733d4abf805adcc7a9bca62175f53968dac1 100644
--- a/chrome/browser/cocoa/browser_window_cocoa.h
+++ b/chrome/browser/cocoa/browser_window_cocoa.h
@@ -90,6 +90,9 @@ class BrowserWindowCocoa : public BrowserWindow,
   // Adds the given FindBar cocoa controller to this browser window.
   void AddFindBar(FindBarCocoaController* find_bar_cocoa_controller);
 
+  // Returns the cocoa-world BrowserWindowController
+  BrowserWindowController* cocoa_controller() { return controller_; }
+
  protected:
   virtual void DestroyBrowser();