Add namespace and re-arrange PDFium's local copy of chromium /base.

third_party/base/logging.h

 // Copyright (c) 2014 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.
 
-#ifndef BASE_LOGGING_H_
-#define BASE_LOGGING_H_
+#ifndef PDFIUM_THIRD_PARTY_BASE_LOGGING_H_
+#define PDFIUM_THIRD_PARTY_BASE_LOGGING_H_
 
 #include <stdlib.h>
 
 #define CHECK(condition)                                                \
   if (!(condition)) {                                                   \
     abort();                                                            \
     *(reinterpret_cast<volatile char*>(NULL) + 42) = 0x42;              \
   }
 
 #define NOTREACHED() abort()
 
-#endif  // BASE_LOGGING_H_
+#endif  // PDFIUM_THIRD_PARTY_BASE_LOGGING_H_