Suppress JavaScript dialogs when a tab puts itself into fullscreen.

chrome/browser/extensions/api/tab_capture/offscreen_tab.h

 // Copyright 2015 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_EXTENSIONS_API_TAB_CAPTURE_OFFSCREEN_TAB_H_
 #define CHROME_BROWSER_EXTENSIONS_API_TAB_CAPTURE_OFFSCREEN_TAB_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 107 matching lines @@
   // Creates the WebContents instance containing the offscreen tab's page,
   // configures it for offscreen rendering at the given |initial_size|, and
   // navigates it to |start_url|.  This is invoked once by OffscreenTabsOwner
   // just after construction.
   void Start(const GURL& start_url,
              const gfx::Size& initial_size,
              const std::string& optional_presentation_id);
 
   // content::WebContentsDelegate overrides to provide the desired behaviors.
   void CloseContents(content::WebContents* source) final;
-  bool ShouldSuppressDialogs(content::WebContents* source) final;
+  bool ShouldSuppressDialogs(content::WebContents* source,
+                             bool before_unload) final;
   bool ShouldFocusLocationBarByDefault(content::WebContents* source) final;
   bool ShouldFocusPageAfterCrash() final;
   void CanDownload(const GURL& url,
                    const std::string& request_method,
                    const base::Callback<void(bool)>& callback) final;
   bool HandleContextMenu(const content::ContextMenuParams& params) final;
   bool PreHandleKeyboardEvent(content::WebContents* source,
                               const content::NativeWebKeyboardEvent& event,
                               bool* is_keyboard_shortcut) final;
   bool PreHandleGestureEvent(content::WebContents* source,
@@ skipping 71 matching lines @@
   // This is false until after the Start() method is called, and capture of the
   // |offscreen_tab_web_contents_| is first detected.
   bool content_capture_was_detected_;
 
   DISALLOW_COPY_AND_ASSIGN(OffscreenTab);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_TAB_CAPTURE_OFFSCREEN_TAB_H_