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

chrome/browser/cocoa/browser_window_controller.h

Index: chrome/browser/cocoa/browser_window_controller.h
diff --git a/chrome/browser/cocoa/browser_window_controller.h b/chrome/browser/cocoa/browser_window_controller.h
index 5ebbbf0053205e7a0fb5436cc0a0371aaf796d1d..671304480bbc18693987f8f2b8b1f554aaccbf81 100644
--- a/chrome/browser/cocoa/browser_window_controller.h
+++ b/chrome/browser/cocoa/browser_window_controller.h
@@ -22,8 +22,10 @@
 class Browser;
 class BrowserWindow;
 class BrowserWindowCocoa;
+class ConstrainedWindowMac;
 @class DownloadShelfController;
 @class FindBarCocoaController;
+@class GTMWindowSheetController;
 @class InfoBarContainerController;
 class LocationBar;
 class StatusBubble;
@@ -137,6 +139,17 @@ class TabStripModelObserverBridge;
 // Delegate method for the status bubble to query about its vertical offset.
 - (float)verticalOffsetForStatusBubble;
 
+// Returns the (lazily created) window sheet controller of this window. Used
+// for the per-tab sheets.
+- (GTMWindowSheetController*)sheetController;
+
+// Checks if there are any tabs with sheets open, and if so, raises one of
+// the tabs with a sheet and returns NO.
+- (BOOL)shouldCloseWithOpenPerTabSheets;
+
+- (void)attachConstrainedWindow:(ConstrainedWindowMac*)window;
+- (void)removeConstrainedWindow:(ConstrainedWindowMac*)window;
+
 @end