Make timeline use the same clock source as mojo's tracing infrastructure

runtime/vm/os_win.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_OS_WINDOWS)
 
 #include "vm/os.h"
 
 #include <malloc.h>  // NOLINT
@@ skipping 103 matching lines @@
   union TimeStamp {
     FILETIME ft_;
     int64_t t_;
   };
   TimeStamp time;
   GetSystemTimeAsFileTime(&time.ft_);
   return (time.t_ - kTimeEpoc) / kTimeScaler;
 }
 
 
+static int64_t qpc_ticks_per_second = 0;
+
+int64_t OS::GetCurrentTraceMicros() {
+  if (qpc_ticks_per_second == 0) {
+    // QueryPerformanceCounter not supported, fallback.
+    return GetCurrentTimeMicros();
+  }
+  // Grab performance counter value.
+  LARGE_INTEGER now;
+  QueryPerformanceCounter(&now);
+  int64_t qpc_value = static_cast<int64_t>(now.QuadPart);
+  // Convert to microseconds.
+  int64_t seconds = qpc_value / qpc_ticks_per_second;
+  int64_t leftover_ticks = qpc_value - (seconds * qpc_ticks_per_second);
+  int64_t result = seconds * kMicrosecondsPerSecond;
+  result += ((leftover_ticks * kMicrosecondsPerSecond) / qpc_ticks_per_second);
+  return result;
+}
+
+
 void* OS::AlignedAllocate(intptr_t size, intptr_t alignment) {
   const int kMinimumAlignment = 16;
   ASSERT(Utils::IsPowerOfTwo(alignment));
   ASSERT(alignment >= kMinimumAlignment);
   void* p = _aligned_malloc(size, alignment);
   if (p == NULL) {
     UNREACHABLE();
   }
   return p;
 }
@@ skipping 209 matching lines @@
   // TODO(5411554): For now we check that initonce is called only once,
   // Once there is more formal mechanism to call InitOnce we can move
   // this check there.
   static bool init_once_called = false;
   ASSERT(init_once_called == false);
   init_once_called = true;
   // Do not pop up a message box when abort is called.
   _set_abort_behavior(0, _WRITE_ABORT_MSG);
   MonitorWaitData::monitor_wait_data_key_ = OSThread::CreateThreadLocal();
   MonitorData::GetMonitorWaitDataForThread();
+  LARGE_INTEGER ticks_per_sec;
+  if (!QueryPerformanceFrequency(&ticks_per_sec)) {
+    qpc_ticks_per_second = 0;
+  } else {
+    qpc_ticks_per_second = static_cast<int64_t>(ticks_per_sec.QuadPart);
+  }
 }
 
 
 void OS::Shutdown() {
 }
 
 
 void OS::Abort() {
   abort();
 }
 
 
 void OS::Exit(int code) {
   exit(code);
 }
 
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)