Revert 124144 - Sync trace time on Chrome OS (just like Android)

Change-Id: I518e0c91a5f48ae1f5909d1e86a8fabfb97d1ec4

BUG=none
TEST=record chrome events using about:tracing simultaneous with kernel events; check the resulting kernel event log for a trace_event_clock_sync record


Review URL: http://codereview.chromium.org/9474023

TBR=sleffler@chromium.org
Review URL: https://chromiumcodereview.appspot.com/9581019

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@124726 0039d316-1c4b-4281-b951-d872f2087c98

base/debug/trace_event_impl.cc

@@ -687,11 +687,11 @@ void TraceLog::AddTraceEventEtw(char phase,
 }
 
 void TraceLog::AddClockSyncMetadataEvents() {
-#if defined(OS_ANDROID) || defined(OS_CHROMEOS)
-  // Since Android/ChromeOS do not support sched_setaffinity, we cannot
-  // establish clock sync unless the scheduler clock is set to global.
-  // If the trace_clock file can't be read, we will assume the kernel
-  // doesn't support tracing and do nothing.
+#if defined(OS_ANDROID)
+  // Since Android does not support sched_setaffinity, we cannot establish clock
+  // sync unless the scheduler clock is set to global. If the trace_clock file
+  // can't be read, we will assume the kernel doesn't support tracing and do
+  // nothing.
   std::string clock_mode;
   if (!file_util::ReadFileToString(
           FilePath("/sys/kernel/debug/tracing/trace_clock"),
@@ -706,7 +706,7 @@ void TraceLog::AddClockSyncMetadataEvents() {
     return;
   }
 
-  // Linux's kernel trace system has a trace_marker feature: this is a file on
+  // Android's kernel trace system has a trace_marker feature: this is a file on
   // debugfs that takes the written data and pushes it onto the trace
   // buffer. So, to establish clock sync, we write our monotonic clock into that
   // trace buffer.