tracing v2: Add base class for zero-copy protobuf (ProtoZero)

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.
 
 # This file is intentionally a gyp file rather than a gypi for dependencies
 # reasons. The other gypi files include content.gyp and content_common depends
 # on this, thus if you try to rename this to gypi and include it in
 # components.gyp, you will get a circular dependency error.
 {
@@ skipping 25 matching lines @@
         'tracing/common/graphics_memory_dump_provider_android.h',
         'tracing/common/process_metrics_memory_dump_provider.cc',
         'tracing/common/process_metrics_memory_dump_provider.h',
         'tracing/common/trace_to_console.cc',
         'tracing/common/trace_to_console.h',
         'tracing/common/tracing_messages.cc',
         'tracing/common/tracing_messages.h',
         'tracing/common/tracing_switches.cc',
         'tracing/common/tracing_switches.h',
         'tracing/core/proto_utils.h',
+        'tracing/core/proto_zero_message.cc',
+        'tracing/core/proto_zero_message.h',
         'tracing/core/scattered_stream_writer.cc',
         'tracing/core/scattered_stream_writer.h',
         'tracing/core/trace_ring_buffer.cc',
         'tracing/core/trace_ring_buffer.h',
         'tracing/tracing_export.h',
       ],
       'target_conditions': [
         ['>(nacl_untrusted_build)==1', {
           'sources!': [
             'tracing/common/process_metrics_memory_dump_provider.cc',
           ],
         }],
       ]
     },
   ],
 }