Revert "Return start/end profiling time in microseconds instead of milliseconds"

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 358 matching lines @@
   OS::Print("root: %u %u %.2fms %.2fms\n",
             root_->total_ticks(), root_->self_ticks(),
             root_->GetTotalMillis(), root_->GetSelfMillis());
 }
 
 
 CpuProfile::CpuProfile(const char* title, unsigned uid, bool record_samples)
     : title_(title),
       uid_(uid),
       record_samples_(record_samples),
-      start_time_us_(OS::Ticks()),
-      end_time_us_(0) {
+      start_time_ms_(OS::TimeCurrentMillis()),
+      end_time_ms_(0) {
 }
 
 
 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_us_ = OS::Ticks();
+  end_time_ms_ = OS::TimeCurrentMillis();
   top_down_.CalculateTotalTicks();
 
-  double duration_ms = (end_time_us_ - start_time_us_) / 1000.;
-  if (duration_ms < 1) duration_ms = 1;
+  double duration = end_time_ms_ - start_time_ms_;
+  if (duration < 1) duration = 1;
   unsigned ticks = top_down_.root()->total_ticks();
-  double rate = ticks / duration_ms;
+  double rate = ticks / duration;
   top_down_.SetTickRatePerMs(rate);
 }
 
 
 void CpuProfile::ShortPrint() {
   OS::Print("top down ");
   top_down_.ShortPrint();
 }
 
 
@@ skipping 295 matching lines @@
     if (no_symbolized_entries) {
       *entry++ = EntryForVMState(sample.state);
     }
   }
 
   profiles_->AddPathToCurrentProfiles(entries);
 }
 
 
 } }  // namespace v8::internal