Add heuristics to limit showing of new backspace UI bubble.

chrome/browser/ui/browser_view_prefs.cc

 // 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.
 
 #include "chrome/browser/ui/browser_view_prefs.h"
 
 #include "build/build_config.h"
 #include "chrome/common/pref_names.h"
 #include "components/pref_registry/pref_registry_syncable.h"
 #include "components/prefs/pref_registry_simple.h"
@@ skipping 18 matching lines @@
   registry->RegisterIntegerPref(kTabStripLayoutType, 0);
   registry->RegisterBooleanPref(prefs::kTabStripStackedLayout, false);
 }
 
 void RegisterBrowserViewProfilePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
   bool custom_frame_default = false;
 #if defined(OS_LINUX) && !defined(OS_CHROMEOS)
   custom_frame_default = ui::GetCustomFramePrefDefault();
 #endif
-
   registry->RegisterBooleanPref(prefs::kUseCustomChromeFrame,
                                 custom_frame_default);
+
+  registry->RegisterIntegerPref(prefs::kBackShortcutBubbleShownCount, 0);
 }
 
 void MigrateBrowserTabStripPrefs(PrefService* prefs) {
   if (prefs->HasPrefPath(kTabStripLayoutType)) {
     prefs->SetBoolean(prefs::kTabStripStackedLayout,
                       prefs->GetInteger(kTabStripLayoutType) != 0);
     prefs->ClearPref(kTabStripLayoutType);
   }
 }
 
 }  // namespace chrome