Add interface to system trace clock.

base/debug/trace_event_impl.cc

 // 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.
 
 #include "base/debug/trace_event_impl.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
@@ skipping 567 matching lines @@
                             const char* name,
                             unsigned long long id,
                             int num_args,
                             const char** arg_names,
                             const unsigned char* arg_types,
                             const unsigned long long* arg_values,
                             int threshold_begin_id,
                             long long threshold,
                             unsigned char flags) {
   DCHECK(name);
-  TimeTicks now = TimeTicks::HighResNow();
+  TimeTicks now = TimeTicks::NowFromSystemTraceTime();
   BufferFullCallback buffer_full_callback_copy;
   int ret_begin_id = -1;
   {
     AutoLock lock(lock_);
     if (!*category_enabled)
       return -1;
     if (logged_events_.size() >= kTraceEventBufferSize)
       return -1;
 
     int thread_id = static_cast<int>(PlatformThread::CurrentId());
@@ skipping 104 matching lines @@
         "The kernel's tracing clock must be set to global in order for " <<
         "trace_event to be synchronized with . Do this by\n" <<
         "  echo global > /sys/kerel/debug/tracing/trace_clock";
     return;
   }
 
   // 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.
-  TimeTicks now = TimeTicks::HighResNow();
+  TimeTicks now = TimeTicks::NowFromSystemTraceTime();
 
   double now_in_seconds = now.ToInternalValue() / 1000000.0;
   std::string marker =
       StringPrintf("trace_event_clock_sync: parent_ts=%f\n",
                    now_in_seconds);
   if (file_util::WriteFile(
           FilePath("/sys/kernel/debug/tracing/trace_marker"),
           marker.c_str(), marker.size()) == -1) {
     DLOG(WARNING) << "Couldn't write to /sys/kernel/debug/tracing/trace_marker";
     return;
@@ skipping 36 matching lines @@
   // Create a FNV hash from the process ID for XORing.
   // See http://isthe.com/chongo/tech/comp/fnv/ for algorithm details.
   unsigned long long offset_basis = 14695981039346656037ull;
   unsigned long long fnv_prime = 1099511628211ull;
   unsigned long long pid = static_cast<unsigned long long>(process_id_);
   process_id_hash_ = (offset_basis ^ pid) * fnv_prime;
 }
 
 }  // namespace debug
 }  // namespace base