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

runtime/include/dart_tools_api.h

 // Copyright (c) 2011, 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.
 
 #ifndef INCLUDE_DART_TOOLS_API_H_
 #define INCLUDE_DART_TOOLS_API_H_
 
 #include "include/dart_api.h"
 
 /** \mainpage Dart Tools Embedding API Reference
@@ skipping 861 matching lines @@
                                                   const char* event_kind,
                                                   const uint8_t* bytes,
                                                   intptr_t bytes_length);
 
 /*
  * ========
  * Timeline
  * ========
  */
 
+/**
+ * Returns a timestamp in microseconds. This timestamp is suitable for
+ * passing into the timeline system.
+ *
+ * \return A timestamp that can be passed to the timeline system.
+ */
+DART_EXPORT int64_t Dart_TimelineGetMicros();
+
 /** Timeline stream for Dart API calls */
 #define DART_TIMELINE_STREAM_API (1 << 0)
 /** Timeline stream for compiler events */
 #define DART_TIMELINE_STREAM_COMPILER (1 << 1)
 /** Timeline stream for embedder provided events */
 #define DART_TIMELINE_STREAM_EMBEDDER (1 << 2)
 /** Timeline stream for GC events */
 #define DART_TIMELINE_STREAM_GC (1 << 3)
 /** Timeline stream for isolate events */
 #define DART_TIMELINE_STREAM_ISOLATE (1 << 4)
@@ skipping 77 matching lines @@
  * \param consumer A Dart_StreamConsumer.
  * \param user_data User data passed into consumer.
  *
  * NOTE: The trace-event format is documented here: https://goo.gl/hDZw5M
  *
  * \return True if a stream was output.
  */
 DART_EXPORT bool Dart_TimelineGetTrace(Dart_StreamConsumer consumer,
                                        void* user_data);
 
-
 /**
  * Get the timeline for entire VM (including all isolates).
  *
  * NOTE: The timeline retrieved from this API call may not include the most
  * recent events.
  *
  * \param consumer A Dart_StreamConsumer.
  * \param user_data User data passed into consumer.
  *
  * NOTE: The trace-event format is documented here: https://goo.gl/hDZw5M
  *
  * \return True if a stream was output.
  */
 DART_EXPORT bool Dart_GlobalTimelineGetTrace(Dart_StreamConsumer consumer,
                                              void* user_data);
 
 /**
  * Add a duration timeline event to the embedder stream for the current isolate.
  *
  * \param label The name of the event.
  * \param start_micros The start of the duration (in microseconds)
  * \param end_micros The end of the duration (in microseconds)
  *
- * NOTE: On Posix platforms you should use gettimeofday and on Windows platforms
- * you should use GetSystemTimeAsFileTime to get the time values.
+ * NOTE: All timestamps should be acquired from Dart_TimelineGetMicros.
  */
 DART_EXPORT Dart_Handle Dart_TimelineDuration(const char* label,
                                               int64_t start_micros,
                                               int64_t end_micros);
 
 
 /**
  * Add an instant timeline event to the embedder stream for the current isolate.
  *
  * \param label The name of event.
  *
- * NOTE: On Posix platforms this call uses gettimeofday and on Windows platforms
- * this call uses GetSystemTimeAsFileTime to get the current time.
+ * NOTE: All timestamps should be acquired from Dart_TimelineGetMicros.
  */
 DART_EXPORT Dart_Handle Dart_TimelineInstant(const char* label);
 
 
 /**
  * Adds an asynchronous begin timeline event to the embedder stream for the
  * current isolate.
  *
  * \param label The name of event.
  *
  * \return Returns an asynchronous id that must be passed to
  * Dart_TimelineAsyncInstant and Dart_TimelineAsyncEnd. If the asynchronous
  * id is less than 0 the event was not added to the timeline and subsequent
  * calls to Dart_TimelineAsyncInstant and Dart_TimelineAsyncEnd will become
  * no-ops.
  *
- * NOTE: On Posix platforms this call uses gettimeofday and on Windows platforms
- * this call uses GetSystemTimeAsFileTime to get the current time.
+ * NOTE: All timestamps should be acquired from Dart_TimelineGetMicros.
  */
 DART_EXPORT Dart_Handle Dart_TimelineAsyncBegin(const char* label,
                                                 int64_t* async_id);
 
 
 /**
  * Adds an asynchronous instant timeline event to the embedder stream for the
  * current isolate.
  *
  * \param label The name of event.
  *
  * \return Returns an asynchronous id that must be passed to
  * Dart_TimelineAsyncInstant and Dart_TimelineAsyncEnd.
  *
- * NOTE: On Posix platforms this call uses gettimeofday and on Windows platforms
- * this call uses GetSystemTimeAsFileTime to get the current time.
+ * NOTE: All timestamps should be acquired from Dart_TimelineGetMicros.
  */
 DART_EXPORT Dart_Handle Dart_TimelineAsyncInstant(const char* label,
                                                   int64_t async_id);
 
 
 /**
  * Adds an asynchronous end timeline event to the embedder stream for the
  * current isolate.
  *
  * \param label The name of event.
  *
  * \return Returns an asynchronous id that must be passed to
  * Dart_TimelineAsyncInstant and Dart_TimelineAsyncEnd.
  *
- * NOTE: On Posix platforms this call uses gettimeofday and on Windows platforms
- * this call uses GetSystemTimeAsFileTime to get the current time.
+ * NOTE: All timestamps should be acquired from Dart_TimelineGetMicros.
  */
 DART_EXPORT Dart_Handle Dart_TimelineAsyncEnd(const char* label,
                                               int64_t async_id);
 
 #endif  // INCLUDE_DART_TOOLS_API_H_