Don't crash when trying to create an ExtensionSyncData from invalid SyncData.

chrome/browser/extensions/extension_sync_data.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_SYNC_DATA_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_SYNC_DATA_H_
 
 #include <string>
 
+#include "base/memory/scoped_ptr.h"
 #include "base/version.h"
 #include "sync/api/sync_change.h"
 #include "url/gurl.h"
 
 namespace syncer {
 class SyncData;
 }
 
 namespace sync_pb {
 class ExtensionSpecifics;
 }
 
 namespace extensions {
 
 class Extension;
 
 // A class that encapsulates the synced properties of an Extension.
 class ExtensionSyncData {
  public:
   enum OptionalBoolean {
     BOOLEAN_UNSET,
     BOOLEAN_TRUE,
     BOOLEAN_FALSE
   };
 
   ExtensionSyncData();
-  explicit ExtensionSyncData(const syncer::SyncData& sync_data);
-  explicit ExtensionSyncData(const syncer::SyncChange& sync_change);
   ExtensionSyncData(const Extension& extension,
                     bool enabled,
                     bool incognito_enabled,
                     bool remote_install,
                     OptionalBoolean all_urls_enabled);
   ~ExtensionSyncData();
 
+  // For constructing an ExtensionSyncData from received sync data.
+  // May return null if the sync data was invalid.
+  static scoped_ptr<ExtensionSyncData> CreateFromSyncData(
+      const syncer::SyncData& sync_data);
+  static scoped_ptr<ExtensionSyncData> CreateFromSyncChange(
+      const syncer::SyncChange& sync_change);
+
   // Retrieve sync data from this class.
   syncer::SyncData GetSyncData() const;
   syncer::SyncChange GetSyncChange(
       syncer::SyncChange::SyncChangeType change_type) const;
 
   // Convert an ExtensionSyncData back out to a sync structure.
   void PopulateExtensionSpecifics(sync_pb::ExtensionSpecifics* specifics) const;
 
-  // Populate this class from sync inputs.
-  void PopulateFromExtensionSpecifics(
+  // Populate this class from sync inputs. Returns true if the input was valid.
+  bool PopulateFromExtensionSpecifics(
       const sync_pb::ExtensionSpecifics& specifics);
 
   void set_uninstalled(bool uninstalled);
 
   const std::string& id() const { return id_; }
 
   // Version-independent properties (i.e., used even when the
   // version of the currently-installed extension doesn't match
   // |version|).
   bool uninstalled() const { return uninstalled_; }
   bool enabled() const { return enabled_; }
   bool incognito_enabled() const { return incognito_enabled_; }
   bool remote_install() const { return remote_install_; }
   OptionalBoolean all_urls_enabled() const { return all_urls_enabled_; }
   bool installed_by_custodian() const { return installed_by_custodian_; }
 
   // Version-dependent properties (i.e., should be used only when the
   // version of the currenty-installed extension matches |version|).
   const Version& version() const { return version_; }
   const GURL& update_url() const { return update_url_; }
   // Used only for debugging.
   const std::string& name() const { return name_; }
 
  private:
   // Populate this class from sync inputs.
-  void PopulateFromSyncData(const syncer::SyncData& sync_data);
+  bool PopulateFromSyncData(const syncer::SyncData& sync_data);
 
   std::string id_;
   bool uninstalled_;
   bool enabled_;
   bool incognito_enabled_;
   bool remote_install_;
   OptionalBoolean all_urls_enabled_;
   bool installed_by_custodian_;
   Version version_;
   GURL update_url_;
   std::string name_;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SYNC_DATA_H_