Split up trace_event.h into trace_event_impl.h and add webkitplatform support.

base/base.gypi

 # 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.
 
 {
   'target_defaults': {
     'variables': {
       'base_target': 0,
     },
     'target_conditions': [
@@ skipping 66 matching lines @@
           'debug/debugger_win.cc',
           'debug/leak_annotations.h',
           'debug/leak_tracker.h',
           'debug/profiler.cc',
           'debug/profiler.h',
           'debug/stack_trace.cc',
           'debug/stack_trace.h',
           'debug/stack_trace_android.cc',
           'debug/stack_trace_posix.cc',
           'debug/stack_trace_win.cc',
-          'debug/trace_event_win.cc',
           'debug/trace_event.cc',
           'debug/trace_event.h',
+          'debug/trace_event_impl.cc',
+          'debug/trace_event_impl.h',
+          'debug/trace_event_win.cc',
           'dir_reader_fallback.h',
           'dir_reader_linux.h',
           'dir_reader_posix.h',
           'eintr_wrapper.h',
           'environment.cc',
           'environment.h',
           'file_descriptor_posix.h',
           'file_path.cc',
           'file_path.h',
           'file_util.cc',
@@ skipping 784 matching lines @@
             'third_party/xdg_mime/xdgmimemagic.c',
             'third_party/xdg_mime/xdgmimemagic.h',
             'third_party/xdg_mime/xdgmimeparent.c',
             'third_party/xdg_mime/xdgmimeparent.h',
           ],
         },
       ],
     }],
   ],
 }