[Reland][Extensions] Don't count bubble focus loss as acknowledgment

chrome/browser/extensions/ntp_overridden_bubble_delegate.cc

 // Copyright (c) 2014 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/extensions/ntp_overridden_bubble_delegate.h"
 
 #include "base/metrics/histogram.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/extension_web_ui.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 111 matching lines @@
 }
 
 void NtpOverriddenBubbleDelegate::LogAction(
     ExtensionMessageBubbleController::BubbleAction action) {
   UMA_HISTOGRAM_ENUMERATION(
       "ExtensionOverrideBubble.NtpOverriddenUserSelection",
       action,
       ExtensionMessageBubbleController::ACTION_BOUNDARY);
 }
 
+const char* NtpOverriddenBubbleDelegate::GetKey() {
+  return "NtpOverriddenBubbleDelegate";
+}
+
 }  // namespace extensions