update_engine: fixed warnings from cpplint

Fixed all the cpplint warnings in update engine.

BUG=None
TEST=Unit tests still pass.

Change-Id: I285ae858eec8abe0b26ff203b99a42a200ceb71c
Reviewed-on: https://chromium-review.googlesource.com/204027
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/mock_file_writer.h b/mock_file_writer.h
index d662871..46e57f4 100644
--- a/mock_file_writer.h
+++ b/mock_file_writer.h
@@ -5,6 +5,8 @@
 #ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_MOCK_FILE_WRITER_H_
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_MOCK_FILE_WRITER_H_
 
+#include <vector>
+
 #include "base/basictypes.h"
 #include "update_engine/file_writer.h"
 
@@ -43,6 +45,7 @@
   const std::vector<char>& bytes() {
     return bytes_;
   }
+
  private:
   // The internal store of all bytes that have been written
   std::vector<char> bytes_;