Add histogram for cancel button in blocked mixed content infobars.

chrome/browser/tab_contents/blocked_infobar_delegate.h

 // Copyright (c) 2011 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_TAB_CONTENTS_BLOCKED_INFOBAR_DELEGATE_H_
 #define CHROME_BROWSER_TAB_CONTENTS_BLOCKED_INFOBAR_DELEGATE_H_
 
 #include "chrome/browser/tab_contents/confirm_infobar_delegate.h"
 #include "chrome/browser/ui/tab_contents/tab_contents_wrapper.h"
 #include "googleurl/src/gurl.h"
@@ skipping 37 matching lines @@
   GURL url_;
 };
 
 // A subclass specific to the blocked displaying insecure content case.
 class BlockedDisplayingInfoBarDelegate : public BlockedInfoBarDelegate {
  public:
   explicit BlockedDisplayingInfoBarDelegate(TabContentsWrapper* wrapper);
  private:
   virtual void InfoBarDismissed() OVERRIDE;
   virtual bool Accept() OVERRIDE;
+  virtual bool Cancel() OVERRIDE;
 };
 
 // A subclass specific to the blocked running insecure content case.
 class BlockedRunningInfoBarDelegate : public BlockedInfoBarDelegate {
  public:
   explicit BlockedRunningInfoBarDelegate(TabContentsWrapper* wrapper);
   virtual BlockedRunningInfoBarDelegate*
       AsBlockedRunningInfoBarDelegate() OVERRIDE;
  private:
   virtual void InfoBarDismissed() OVERRIDE;
   virtual bool Accept() OVERRIDE;
+  virtual bool Cancel() OVERRIDE;
 };
 
 #endif  // CHROME_BROWSER_TAB_CONTENTS_BLOCKED_INFOBAR_DELEGATE_H_