[Mac] Prevent constrained windows (sheets) from opening while instant preview...

chrome/browser/cocoa/browser_window_controller.h

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_COCOA_BROWSER_WINDOW_CONTROLLER_H_
 #define CHROME_BROWSER_COCOA_BROWSER_WINDOW_CONTROLLER_H_
 #pragma once
 
 // A class acting as the Objective-C controller for the Browser
 // object. Handles interactions between Cocoa and the cross-platform
@@ skipping 216 matching lines @@
 
 // Returns the (lazily created) window sheet controller of this window. Used
 // for the per-tab sheets.
 - (GTMWindowSheetController*)sheetController;
 
 // Requests that |window| is opened as a per-tab sheet to the current tab.
 - (void)attachConstrainedWindow:(ConstrainedWindowMac*)window;
 // Closes the tab sheet |window| and potentially shows the next sheet in the
 // tab's sheet queue.
 - (void)removeConstrainedWindow:(ConstrainedWindowMac*)window;
+// Returns NO if constrained windows cannot be attached to this window.
+- (BOOL)canAttachConstrainedWindow;
 
 // Shows or hides the docked web inspector depending on |contents|'s state.
 - (void)updateDevToolsForContents:(TabContents*)contents;
 
 // Displays the active sidebar linked to the |contents| or hides sidebar UI,
 // if there's no such sidebar.
 - (void)updateSidebarForContents:(TabContents*)contents;
 
 // Gets the current theme provider.
 - (ThemeProvider*)themeProvider;
@@ skipping 139 matching lines @@
 - (void)resetWindowGrowthState;
 
 // Computes by how far in each direction, horizontal and vertical, the
 // |source| rect doesn't fit into |target|.
 - (NSSize)overflowFrom:(NSRect)source
                     to:(NSRect)target;
 @end  // @interface BrowserWindowController(TestingAPI)
 
 
 #endif  // CHROME_BROWSER_COCOA_BROWSER_WINDOW_CONTROLLER_H_