Add events with custom timestamps and thread id to PPAPI dev tracing interface.

ppapi/api/dev/ppb_trace_event_dev.idl

Index: ppapi/api/dev/ppb_trace_event_dev.idl
diff --git a/ppapi/api/dev/ppb_trace_event_dev.idl b/ppapi/api/dev/ppb_trace_event_dev.idl
index ff01dea32859d6a62fa476a5b4b4b31d6a3556f5..8e483cd6e824e08f7b570b2d843c87ea88ae18d4 100644
--- a/ppapi/api/dev/ppb_trace_event_dev.idl
+++ b/ppapi/api/dev/ppb_trace_event_dev.idl
@@ -9,9 +9,15 @@
  */
 
 label Chrome {
-  M25 = 0.1
+  M25 = 0.1,
+  M29 = 0.2
 };
 
+/**
+ * A trace event timestamp.
+ */
+typedef int64_t PP_TraceEventTime;
+
 interface PPB_Trace_Event_Dev {
   /**
    * Gets a pointer to a character for identifying a category name in the
@@ -43,6 +49,34 @@ interface PPB_Trace_Event_Dev {
       [in] uint8_t flags);
 
   /**
+   * Version of the above interface that allows specifying a custom thread id
+   * and timestamp. This is useful for when tracing data cannot be registered
+   * in real time. For example, this could be used by storing timestamps
+   * internally and then registering the events retroactively.
+   */
+  [version=0.2]
+  void AddTraceEventWithThreadIdAndTimestamp(
+      [in] int8_t phase,
+      [in] mem_t category_enabled,
+      [in] cstr_t name,
+      [in] uint64_t id,
+      [in] int32_t thread_id,
+      [in] PP_TraceEventTime timestamp,
+      [in] uint32_t num_args,
+      [in, size_as=num_args] str_t[] arg_names,
+      [in, size_as=num_args] uint8_t[] arg_types,
+      [in, size_as=num_args] uint64_t[] arg_values,
+      [in] uint8_t flags);
+
+  /**
+   * Get the current clock value. Since this uses the same function as the trace
+   * events use internally, it can be used to create events with explicit time
+   * stamps.
+   */
+  [version=0.2]
+  PP_TraceEventTime Now();
+
+  /**
    * Sets the thread name of the calling thread in the tracing system so it will
    * show up properly in chrome://tracing.
    */