Trace PostTasks from post to run

base/debug/trace_event.h

Index: base/debug/trace_event.h
diff --git a/base/debug/trace_event.h b/base/debug/trace_event.h
index 804b468116243bf17674fd64002f4ababf1c1ea0..d74f861a455737d67373ab2c8a1a22aeefaa1684 100644
--- a/base/debug/trace_event.h
+++ b/base/debug/trace_event.h
@@ -162,6 +162,11 @@
 #define TRACE_STR_COPY(str) \
     trace_event_internal::TraceStringWithCopy(str)
 
+// By default, uint64 ID argument values are not mangled with the Process ID in
+// TRACE_EVENT_ASYNC macros. Use this macro to force Process ID mangling.
+#define TRACE_ID_MANGLE(id) \
+    trace_event_internal::TraceID::ForceMangle(id)
+
 // Records a pair of begin and end events called "name" for the current
 // scope, with 0, 1 or 2 associated arguments. If the category is not
 // enabled, then this does nothing.
@@ -638,11 +643,38 @@ const unsigned long long kNoEventId = 0;
 // same pointer is used on different processes.
 class TraceID {
  public:
+  class ForceMangle {
+    public:
+     explicit ForceMangle(unsigned long long id) : data_(id) {}
+     explicit ForceMangle(unsigned long id) : data_(id) {}
+     explicit ForceMangle(unsigned int id) : data_(id) {}
+     explicit ForceMangle(unsigned short id) : data_(id) {}
+     explicit ForceMangle(unsigned char id) : data_(id) {}
+     explicit ForceMangle(long long id) :
+         data_(static_cast<unsigned long long>(id)) {}
+     explicit ForceMangle(long id) :
+         data_(static_cast<unsigned long long>(id)) {}
+     explicit ForceMangle(int id) :
+         data_(static_cast<unsigned long long>(id)) {}
+     explicit ForceMangle(short id) :
+         data_(static_cast<unsigned long long>(id)) {}
+     explicit ForceMangle(signed char id) :
+         data_(static_cast<unsigned long long>(id)) {}
+
+     unsigned long long data() const { return data_; }
+
+    private:
+     unsigned long long data_;
+  };
+
   explicit TraceID(const void* id, unsigned char* flags) :
       data_(static_cast<unsigned long long>(
           reinterpret_cast<unsigned long>(id))) {
     *flags |= TRACE_EVENT_FLAG_MANGLE_ID;
   }
+  explicit TraceID(ForceMangle id, unsigned char* flags) : data_(id.data()) {
+    *flags |= TRACE_EVENT_FLAG_MANGLE_ID;
+  }
   explicit TraceID(unsigned long long id, unsigned char* flags) :
       data_(id) { (void)flags; }
   explicit TraceID(unsigned long id, unsigned char* flags) :