Make base::PendingTask support ConvertableToTraceFormat

base/trace_event/trace_event.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_TRACE_EVENT_TRACE_EVENT_H_
 #define BASE_TRACE_EVENT_TRACE_EVENT_H_
 
 // This header file defines implementation details of how the trace macros in
 // trace_event_common.h collect and store trace events. Anything not
 // implementation-specific should go in trace_event_common.h instead of here.
@@ skipping 420 matching lines @@
     /* Local class friendly DISALLOW_COPY_AND_ASSIGN */                    \
     INTERNAL_TRACE_EVENT_UID(ScopedContext)                                \
     (const INTERNAL_TRACE_EVENT_UID(ScopedContext)&) {};                   \
     void operator=(const INTERNAL_TRACE_EVENT_UID(ScopedContext)&) {};     \
   };                                                                       \
   INTERNAL_TRACE_EVENT_UID(ScopedContext)                                  \
   INTERNAL_TRACE_EVENT_UID(scoped_context)(context);
 
 // Implementation detail: internal macro to trace a task execution with the
 // location where it was posted from.
-#define INTERNAL_TRACE_TASK_EXECUTION(run_function, task)                 \
-  TRACE_EVENT2("toplevel", run_function, "src_file",                      \
-               (task).posted_from.file_name(), "src_func",                \
-               (task).posted_from.function_name());                       \
-  TRACE_HEAP_PROFILER_API_SCOPED_TASK_EXECUTION INTERNAL_TRACE_EVENT_UID( \
+#define INTERNAL_TRACE_TASK_EXECUTION(run_function, task)                      \

[Sami, 2016/10/04 11:25:31]

I believe there are a number of tools (e.g., Lighthouse, maybe also Telemetry)
that parse this information. Could we try to track them down and coordinate this
change with them?

+  TRACE_EVENT1("toplevel", run_function, "src_info", (task).GetTracingInfo()); \
+  TRACE_HEAP_PROFILER_API_SCOPED_TASK_EXECUTION INTERNAL_TRACE_EVENT_UID(      \
       task_event)((task).posted_from.file_name());
 
 namespace trace_event_internal {
 
 // Specify these values when the corresponding argument of AddTraceEvent is not
 // used.
 const int kZeroNumArgs = 0;
 const std::nullptr_t kGlobalScope = nullptr;
 const unsigned long long kNoId = 0;
 
@@ skipping 703 matching lines @@
   const char* name_;
   IDType id_;
 
   DISALLOW_COPY_AND_ASSIGN(TraceScopedTrackableObject);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_TRACE_EVENT_H_