Moving platform tracing things into platform/tracing.

third_party/WebKit/Source/platform/tracing/TraceEventCommon.h

 // Copyright 2015 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 header file defines the set of trace_event macros without specifying
 // how the events actually get collected and stored. If you need to expose trace
 // events to some other universe, you can copy-and-paste this file as well as
 // trace_event.h, modifying the macros contained there as necessary for the
 // target platform. The end result is that multiple libraries can funnel events
 // through to a shared trace event collector.
 
 // IMPORTANT: To avoid conflicts, if you need to modify this file for a library,

[haraken, 2016/09/16 07:51:32]

Ditto. We should unify the tracing macros with Chromium and remove
TraceEventCommon.h entirely.

 // land your change in base/ first, and then copy-and-paste it.
 
 // Trace events are for tracking application performance and resource usage.
 // Macros are provided to track:
 //    Begin and end of function calls
 //    Counters
 //
 // Events are issued against categories. Whereas LOG's
 // categories are statically defined, TRACE categories are created
 // implicitly with a string. For example:
@@ skipping 1018 matching lines @@
 
 // Enum reflecting the scope of an INSTANT event. Must fit within
 // TRACE_EVENT_FLAG_SCOPE_MASK.
 #define TRACE_EVENT_SCOPE_GLOBAL (static_cast<unsigned char>(0 << 3))
 #define TRACE_EVENT_SCOPE_PROCESS (static_cast<unsigned char>(1 << 3))
 #define TRACE_EVENT_SCOPE_THREAD (static_cast<unsigned char>(2 << 3))
 
 #define TRACE_EVENT_SCOPE_NAME_GLOBAL ('g')
 #define TRACE_EVENT_SCOPE_NAME_PROCESS ('p')
 #define TRACE_EVENT_SCOPE_NAME_THREAD ('t')