components: Fix components_tracing.gyp to follow the same pattern of the other gyp files.

components/tracing.gyp

 # 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.
 
 {

[Jói, 2013/03/08 02:22:45]

Suggest adding a comment here, explaining that if you try to move this to
tracing.gypi and include it in components.gyp, you will get the circular
dependency error.

[tfarina, 2013/03/08 02:30:08]

Done.

   'targets' : [
     {
       'target_name': 'tracing',
       'type': 'static_library',
       'defines!': ['CONTENT_IMPLEMENTATION'],
       'dependencies': [
         '../base/base.gyp:base',
         '../ipc/ipc.gyp:ipc',
       ],
       'include_dirs': [
         '..',
       ],
       'sources': [
         'tracing/child_trace_message_filter.cc',
         'tracing/child_trace_message_filter.h',
         'tracing/tracing_messages.cc',
         'tracing/tracing_messages.h',
       ],
     },
   ],
 }