Use stricter type checking in UMA_HISTOGRAM_ENUMERATION

components/sync/model/data_type_error_handler_impl.cc

 // Copyright 2016 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 "components/sync/model/data_type_error_handler_impl.h"
 
 #include "base/bind.h"
 #include "base/metrics/histogram_macros.h"
 
 namespace syncer {
 
 DataTypeErrorHandlerImpl::DataTypeErrorHandlerImpl(
     const scoped_refptr<base::SingleThreadTaskRunner>& ui_thread,
     const base::Closure& dump_stack,
     const ErrorCallback& sync_callback)
     : ui_thread_(ui_thread),
       dump_stack_(dump_stack),
       sync_callback_(sync_callback) {}
 
 DataTypeErrorHandlerImpl::~DataTypeErrorHandlerImpl() {}
 
 void DataTypeErrorHandlerImpl::OnUnrecoverableError(const SyncError& error) {
   if (!dump_stack_.is_null())
     dump_stack_.Run();
+  // TODO(wychen): enum uma should be strongly typed. crbug.com/661401
   UMA_HISTOGRAM_ENUMERATION("Sync.DataTypeRunFailures",
                             ModelTypeToHistogramInt(error.model_type()),
-                            MODEL_TYPE_COUNT);
+                            static_cast<int>(MODEL_TYPE_COUNT));
   ui_thread_->PostTask(error.location(), base::Bind(sync_callback_, error));
 }
 
 SyncError DataTypeErrorHandlerImpl::CreateAndUploadError(
     const tracked_objects::Location& location,
     const std::string& message,
     ModelType type) {
   if (!dump_stack_.is_null())
     dump_stack_.Run();
   return SyncError(location, SyncError::DATATYPE_ERROR, message, type);
 }
 
 std::unique_ptr<DataTypeErrorHandler> DataTypeErrorHandlerImpl::Copy() const {
   return base::MakeUnique<DataTypeErrorHandlerImpl>(ui_thread_, dump_stack_,
                                                     sync_callback_);
 }
 
 }  // namespace syncer