Fix content verification code for undreadable and deleted files.

extensions/browser/scoped_ignore_content_verifier_for_test.h

 // Copyright 2016 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 EXTENSIONS_BROWSER_SCOPED_IGNORE_CONTENT_VERIFIER_FOR_TEST_H_
 #define EXTENSIONS_BROWSER_SCOPED_IGNORE_CONTENT_VERIFIER_FOR_TEST_H_
 
 #include <string>
 
 #include "extensions/browser/content_verify_job.h"
 
 namespace extensions {
 
 // A class for use in tests to make content verification failures be ignored
 // during the lifetime of an instance of it. Note that only one instance should
 // be alive at any given time, and that it is not compatible with other
 // concurrent objects using the ContentVerifyJob::TestDelegate interface.
 class ScopedIgnoreContentVerifierForTest
     : public ContentVerifyJob::TestDelegate {
  public:
   ScopedIgnoreContentVerifierForTest();
-  ~ScopedIgnoreContentVerifierForTest();
+  ~ScopedIgnoreContentVerifierForTest() override;
 
   // ContentVerifyJob::TestDelegate interface
   ContentVerifyJob::FailureReason BytesRead(const std::string& extension_id,
                                             int count,
                                             const char* data) override;
   ContentVerifyJob::FailureReason DoneReading(
       const std::string& extension_id) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ScopedIgnoreContentVerifierForTest);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_SCOPED_IGNORE_CONTENT_VERIFIER_FOR_TEST_H_