Add API to get the VM global timeline

runtime/include/dart_tools_api.h

Index: runtime/include/dart_tools_api.h
diff --git a/runtime/include/dart_tools_api.h b/runtime/include/dart_tools_api.h
index 64991285f7b3d137cfeccbcb9473675d3dbd83a5..0ed7cd28aee08c958ee82f6d7630a9fbc155ba33 100644
--- a/runtime/include/dart_tools_api.h
+++ b/runtime/include/dart_tools_api.h
@@ -976,6 +976,23 @@ typedef void (*Dart_StreamConsumer)(
 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.
  *