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

chrome/browser/value_store/value_store.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_VALUE_STORE_VALUE_STORE_H_
 #define CHROME_BROWSER_VALUE_STORE_VALUE_STORE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 59 matching lines @@
 
   // The result of a read operation (Get).
   class ReadResultType {
    public:
     explicit ReadResultType(scoped_ptr<base::DictionaryValue> settings);
     explicit ReadResultType(scoped_ptr<Error> error);
     ~ReadResultType();
 
     bool HasError() const { return error_; }
 
+    bool IsCorruption() const {

[Matt Perry, 2014/02/19 01:34:22]

opt: HasCorruption or IsCorrupted would sound better IMO

[Devlin, 2014/02/19 17:43:19]

I've no preference, but I think Ben originally suggested IsCorruption() so it
matches the very-similar leveldb call. [1]  But if he doesn't care either, I'm
happy to change it to IsCorrupted().

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/leveld...

[Devlin, 2014/02/19 17:48:52]

Done.

+      return error_.get() && error_->code == CORRUPTION;
+    }
+
     // Gets the settings read from the storage. Note that this represents
     // the root object. If you request the value for key "foo", that value will
     // be in |settings|.|foo|.
     //
     // Must only be called if there is no error.
     base::DictionaryValue& settings() { return *settings_; }
     scoped_ptr<base::DictionaryValue> PassSettings() {
       return settings_.Pass();
     }
 
@@ skipping 94 matching lines @@
       WriteOptions options, const base::DictionaryValue& values) = 0;
 
   // Removes a key from the storage.
   virtual WriteResult Remove(const std::string& key) = 0;
 
   // Removes multiple keys from the storage.
   virtual WriteResult Remove(const std::vector<std::string>& keys) = 0;
 
   // Clears the storage.
   virtual WriteResult Clear() = 0;
+
+  // In the event of corruption, the ValueStore should be able to restore
+  // itself. This means deleting local corrupted files. If only a few keys are
+  // corrupted, then some of the database may be saved. If the full database is
+  // corrupted, this will erase it in its entirety.
+  // Returns true on success, false on failure. The only way this will fail is
+  // if we also cannot delete the database file.
+  // Note: This method needs to read (and possibly delete) the whole database,
+  // so it is slow and should be used sparingly.
+  // Note: This method (and the following RestoreKey()) are rude, and do not
+  // make any logs, track changes, or other generally polite things. Please do
+  // not use these as substitutes for Clear() and Remove().
+  virtual bool Restore() = 0;
+
+  // Similar to Restore(), but for only a particular key. If the key is corrupt,
+  // this will forcefully remove the key. It does not look at the database on
+  // the whole, which makes it faster, but does not guarantee there is no
+  // additional corruption.
+  // Returns true on success, and false on failure. If false, the next step is
+  // probably to Restore() the whole database.
+  virtual bool RestoreKey(const std::string& key) = 0;
 };
 
 #endif  // CHROME_BROWSER_VALUE_STORE_VALUE_STORE_H_