Switch CPU profile start/stop markers to monotonic time.

src/profile-generator.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 337 matching lines @@
       // Remove child from the stack.
       stack.RemoveLast();
     }
   }
 }
 
 
 CpuProfile::CpuProfile(const char* title, bool record_samples)
     : title_(title),
       record_samples_(record_samples),
-      start_time_(Time::NowFromSystemTime()) {
-  timer_.Start();
+      start_time_(TimeTicks::HighResolutionNow()) {
 }
 
 
 void CpuProfile::AddPath(const Vector<CodeEntry*>& path) {
   ProfileNode* top_frame_node = top_down_.AddPathFromEnd(path);
   if (record_samples_) samples_.Add(top_frame_node);
 }
 
 
 void CpuProfile::CalculateTotalTicksAndSamplingRate() {
-  end_time_ = start_time_ + timer_.Elapsed();
+  end_time_ = TimeTicks::HighResolutionNow();
 }
 
 
 void CpuProfile::Print() {
   OS::Print("[Top down]:\n");
   top_down_.Print();
 }
 
 
 CodeEntry* const CodeMap::kSharedFunctionCodeEntry = NULL;
@@ skipping 310 matching lines @@
     case OTHER:
     case EXTERNAL:
       return program_entry_;
     case IDLE:
       return idle_entry_;
     default: return NULL;
   }
 }
 
 } }  // namespace v8::internal