gdata: Fix a bug that caused google drive not to load

chrome/browser/chromeos/gdata/gdata_files.cc

 // 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.
 
 #include "chrome/browser/chromeos/gdata/gdata_files.h"
 
 #include "base/utf_string_conversions.h"
 #include "base/platform_file.h"
 #include "base/stringprintf.h"
 #include "base/string_util.h"
@@ skipping 848 matching lines @@
   ToProto(proto.get());
   const bool ok = proto->SerializeToString(serialized_proto);
   DCHECK(ok);
 }
 
 bool GDataRootDirectory::ParseFromString(const std::string& serialized_proto) {
   scoped_ptr<GDataRootDirectoryProto> proto(
       new GDataRootDirectoryProto());
   bool ok = proto->ParseFromString(serialized_proto);
   if (ok) {
+    // The title field for the root directory was originally empty, then
+    // changed to "gdata", then changed to "drive". Discard the proto data if
+    // the older formats are detected. See crbug.com/128133 for details.
+    const std::string& title = proto->gdata_directory().gdata_entry().title();
+    if (title != "drive") {
+      LOG(ERROR) << "Incompatible proto detected: " << title;
+      return false;
+    }
+
     FromProto(*proto.get());
     set_origin(FROM_CACHE);
     set_refresh_time(base::Time::Now());
   }
   return ok;
 }
 
 }  // namespace gdata