Fix crash by preventing extensions from changing their IDs.

chrome/common/extensions/extension_constants.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_COMMON_EXTENSIONS_EXTENSION_CONSTANTS_H_
 #define CHROME_COMMON_EXTENSIONS_EXTENSION_CONSTANTS_H_
 #pragma once
 
 #include <string>
 
@@ skipping 120 matching lines @@
   extern const char* kRunAtDocumentEnd;
   extern const char* kRunAtDocumentIdle;
   extern const char* kRunAtDocumentStart;
 }  // namespace extension_manifest_values
 
 // Error messages returned from Extension::InitFromValue().
 namespace extension_manifest_errors {
   extern const char* kAppsNotEnabled;
   extern const char* kBackgroundPermissionNeeded;
   extern const char* kCannotAccessPage;
+  extern const char* kCannotChangeExtensionID;
   extern const char* kCannotClaimAllHostsInExtent;
   extern const char* kCannotClaimAllURLsInExtent;
   extern const char* kCannotScriptGallery;
   extern const char* kCannotUninstallManagedExtension;
   extern const char* kChromeVersionTooLow;
   extern const char* kDevToolsExperimental;
   extern const char* kDisabledByPolicy;
   extern const char* kExperimentalFlagRequired;
   extern const char* kExperimentalFeature;
   extern const char* kExpectString;
@@ skipping 305 matching lines @@
   };
 
   enum UnloadedExtensionReason {
     UNLOAD_REASON_DISABLE,    // Extension is being disabled.
     UNLOAD_REASON_UPDATE,     // Extension is being updated to a newer version.
     UNLOAD_REASON_UNINSTALL,  // Extension is being uninstalled.
   };
 } // extension_misc
 
 #endif  // CHROME_COMMON_EXTENSIONS_EXTENSION_CONSTANTS_H_