Add a Restore() method to ValueStore and make StorageAPI use it

chrome/browser/extensions/api/storage/storage_api.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_API_STORAGE_STORAGE_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_STORAGE_STORAGE_API_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "chrome/browser/extensions/api/storage/settings_namespace.h"
@@ skipping 12 matching lines @@
   // ExtensionFunction:
   virtual bool ShouldSkipQuotaLimiting() const OVERRIDE;
   virtual bool RunImpl() OVERRIDE;
 
   // Extension settings function implementations should do their work here.
   // The SettingsFrontend makes sure this is posted to the appropriate thread.
   // Implementations should fill in args themselves, though (like RunImpl)
   // may return false to imply failure.
   virtual bool RunWithStorage(ValueStore* storage) = 0;
 
-  // Sets error_ or result_ depending on the value of a storage ReadResult, and
-  // returns whether the result implies success (i.e. !error).
-  bool UseReadResult(ValueStore::ReadResult result);
+  // Handles the |result| of a read function.
+  // - If the result succeeded, this will set |result_| and return.
+  // - If |result| failed with a ValueStore::CORRUPTION error, this will call
+  //   RestoreStorageAndRetry(), and return that result.
+  // - If the |result| failed with a different error, this will set |error_|
+  //   and return.
+  bool UseReadResult(ValueStore::ReadResult result, ValueStore* storage);
 
-  // Sets error_ depending on the value of a storage WriteResult, sends a
-  // change notification if needed, and returns whether the result implies
-  // success (i.e. !error).
-  bool UseWriteResult(ValueStore::WriteResult result);
+  // Handles the |result| of a write function.
+  // - If the result succeeded, this will set |result_| and return.
+  // - If |result| failed with a ValueStore::CORRUPTION error, this will call
+  //   RestoreStorageAndRetry(), and return that result.
+  // - If the |result| failed with a different error, this will set |error_|
+  //   and return.
+  // This will also send out a change notification, if appropriate.
+  bool UseWriteResult(ValueStore::WriteResult result, ValueStore* storage);
 
  private:
   // Called via PostTask from RunImpl.  Calls RunWithStorage and then
   // SendResponse with its success value.
   void AsyncRunWithStorage(ValueStore* storage);
 
+  // Called if we encounter a ValueStore error. If the error is due to
+  // corruption, tries to restore the ValueStore and re-run the API function.
+  // If the storage cannot be restored or was due to some other error, then sets
+  // error and returns. This also sets the |tried_restoring_storage_| flag to
+  // ensure we don't enter a loop.
+  bool HandleError(const ValueStore::Error& error, ValueStore* storage);
+
   // The settings namespace the call was for.  For example, SYNC if the API
   // call was chrome.settings.experimental.sync..., LOCAL if .local, etc.
   settings_namespace::Namespace settings_namespace_;
 
+  // A flag indicating whether or not we have tried to restore storage. We
+  // should only ever try once (per API call) in order to avoid entering a loop.
+  bool tried_restoring_storage_;
+
   // Observers, cached so that it's only grabbed from the UI thread.
   scoped_refptr<SettingsObserverList> observers_;
 };
 
 class StorageStorageAreaGetFunction : public SettingsFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("storage.get", STORAGE_GET)
 
  protected:
   virtual ~StorageStorageAreaGetFunction() {}
@@ skipping 54 matching lines @@
  protected:
   virtual ~StorageStorageAreaGetBytesInUseFunction() {}
 
   // SettingsFunction:
   virtual bool RunWithStorage(ValueStore* storage) OVERRIDE;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_STORAGE_STORAGE_API_H_