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

chrome/browser/value_store/testing_value_store.cc

Index: chrome/browser/value_store/testing_value_store.cc
diff --git a/chrome/browser/value_store/testing_value_store.cc b/chrome/browser/value_store/testing_value_store.cc
index c8d177c55147d5f26d0d2ef15853853dbc36cc4d..d6ef91a09bb8293afff3ca7276faa714fd41a9fe 100644
--- a/chrome/browser/value_store/testing_value_store.cc
+++ b/chrome/browser/value_store/testing_value_store.cc
@@ -124,6 +124,29 @@ ValueStore::WriteResult TestingValueStore::Clear() {
   return Remove(keys);
 }
 
+bool TestingValueStore::Restore() {
+  ReadResult result = Get();
+  std::string previous_key;
+  while (result->IsCorruption()) {
+    if (!result->error().key.get() || *result->error().key == previous_key ||
+        !RestoreKey(*result->error().key)) {
+      Clear();
+      result = Get();
+      break;
+    }
+    previous_key = *result->error().key;
+    result = Get();
+  }
+  return !result->IsCorruption();
+}
+
+bool TestingValueStore::RestoreKey(const std::string& key) {
+  ReadResult result = Get(key);
+  if (result->IsCorruption())
+    Remove(key);
+  return !Get(key)->IsCorruption();
+}
+
 scoped_ptr<ValueStore::Error> TestingValueStore::TestingError() {
   return make_scoped_ptr(new ValueStore::Error(
       error_code_, kGenericErrorMessage, scoped_ptr<std::string>()));