Add heuristics to limit showing of new backspace UI bubble.

chrome/test/base/test_browser_window.h

 // Copyright (c) 2012 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_TEST_BASE_TEST_BROWSER_WINDOW_H_
 #define CHROME_TEST_BASE_TEST_BROWSER_WINDOW_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "build/build_config.h"
@@ skipping 49 matching lines @@
   gfx::Rect GetBounds() const override;
   gfx::Size GetContentsSize() const override;
   bool IsMaximized() const override;
   bool IsMinimized() const override;
   void Maximize() override {}
   void Minimize() override {}
   void Restore() override {}
   bool ShouldHideUIForFullscreen() const override;
   bool IsFullscreen() const override;
   bool IsFullscreenBubbleVisible() const override;
-  void ShowNewBackShortcutBubble(bool forward) override;
+  void MaybeShowNewBackShortcutBubble(bool forward) override {}
+  void HideNewBackShortcutBubble() override {}
   LocationBar* GetLocationBar() const override;
   void SetFocusToLocationBar(bool select_all) override {}
   void UpdateReloadStopState(bool is_loading, bool force) override {}
   void UpdateToolbar(content::WebContents* contents) override {}
   void ResetToolbarTabState(content::WebContents* contents) override {}
   void FocusToolbar() override {}
   ToolbarActionsBar* GetToolbarActionsBar() override;
   void ToolbarSizeChanged(bool is_animating) override {}
   void FocusAppMenu() override {}
   void FocusBookmarksToolbar() override {}
@@ skipping 121 matching lines @@
 
 namespace chrome {
 
 // Helper that handle the lifetime of TestBrowserWindow instances.
 std::unique_ptr<Browser> CreateBrowserWithTestWindowForParams(
     Browser::CreateParams* params);
 
 }  // namespace chrome
 
 #endif  // CHROME_TEST_BASE_TEST_BROWSER_WINDOW_H_