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

chrome/browser/extensions/api/storage/policy_value_store.cc

Index: chrome/browser/extensions/api/storage/policy_value_store.cc
diff --git a/chrome/browser/extensions/api/storage/policy_value_store.cc b/chrome/browser/extensions/api/storage/policy_value_store.cc
index f5da68205785a23105b728cac0fa2feef3c39eba..9691e2bf01c832a43b7e6db4d6c8710d2d7858f6 100644
--- a/chrome/browser/extensions/api/storage/policy_value_store.cc
+++ b/chrome/browser/extensions/api/storage/policy_value_store.cc
@@ -57,6 +57,17 @@ void PolicyValueStore::SetCurrentPolicy(const policy::PolicyMap& policy) {
   // must be removed.
   base::DictionaryValue previous_policy;
   ValueStore::ReadResult read_result = delegate_->Get();
+
+  // If the database is corrupted, try to restore it.
+  // This may have the unfortunate side-effect of incorrectly informing the
+  // extension of a "new" key, which isn't new and was corrupted. Unfortunately,
+  // there's not always a way around this - if the database is corrupted, there
+  // may be no way of telling which keys were previously present.
+  if (read_result->IsCorrupted()) {
+    if (delegate_->Restore())
+      read_result = delegate_->Get();
+  }
+
   if (read_result->HasError()) {
     LOG(WARNING) << "Failed to read managed settings for extension "
         << extension_id_ << ": " << read_result->error().message;
@@ -161,4 +172,10 @@ ValueStore::WriteResult PolicyValueStore::Clear() {
   return MakeWriteResult(ReadOnlyError(util::NoKey()));
 }
 
+bool PolicyValueStore::Restore() { return delegate_->Restore(); }
+
+bool PolicyValueStore::RestoreKey(const std::string& key) {
+  return delegate_->RestoreKey(key);
+}
+
 }  // namespace extensions