Mac: the return of the tab-modal-sheets patch.

chrome/browser/tab_contents/constrained_window.h

Index: chrome/browser/tab_contents/constrained_window.h
diff --git a/chrome/browser/tab_contents/constrained_window.h b/chrome/browser/tab_contents/constrained_window.h
index 057ee2745f56e3b1caa5984f21857166dcc0b58b..4f90cc89eb55839dd6523705bad55446458d17f1 100644
--- a/chrome/browser/tab_contents/constrained_window.h
+++ b/chrome/browser/tab_contents/constrained_window.h
@@ -41,6 +41,21 @@ class ConstrainedWindow {
 
   // Closes the Constrained Window.
   virtual void CloseConstrainedWindow() = 0;
+
+  // Events which constrained windows may recognize.
+  enum Event {
+    kEventNavigate,
+  };
+
+  // Inform the constrained the window that its parent tab will do something.
+  // Returns |true| if it did something in response, |false| if not. The default
+  // implementation, appropriate for "content-area" constrained windows, does
+  // the following:
+  //  - |kEventNavigate|: calls |CloseConstrainedWindow()|;
+  //  - anything/everything else: nothing.
+  // Platforms which implement non-"content-area" constrained windows (e.g.,
+  // tab-modal open/close dialogs) should override this.
+  virtual bool ParentWillDo(Event event);
 };
 
 #endif  // CHROME_BROWSER_TAB_CONTENTS_CONSTRAINED_WINDOW_H_