Review and cleanup lint warnings.

testing/test_support.cpp

 // Copyright 2015 PDFium 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 "testing/test_support.h"
 
 #include <stdio.h>
 #include <string.h>
 
+#include <string>
+
 #include "testing/utils/path_service.h"
 
 #ifdef PDF_ENABLE_V8
 #include "v8/include/libplatform/libplatform.h"
 #endif
 
 namespace {
 
 #ifdef PDF_ENABLE_V8
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
@@ skipping 163 matching lines @@
 }
 
 // static
 int TestSaver::WriteBlockCallback(FPDF_FILEWRITE* pFileWrite,
                                   const void* data,
                                   unsigned long size) {
   TestSaver* pThis = static_cast<TestSaver*>(pFileWrite);
   pThis->m_String.append(static_cast<const char*>(data), size);
   return 1;
 }