tracing: fix edge case when dumping while trace being disabled

base/trace_event/memory_dump_manager.h

Index: base/trace_event/memory_dump_manager.h
diff --git a/base/trace_event/memory_dump_manager.h b/base/trace_event/memory_dump_manager.h
index b3880afdf478e4f7abbadd119515f832427fe749..9d5f07b35c7e551b5e01b7cc524682f03a745a66 100644
--- a/base/trace_event/memory_dump_manager.h
+++ b/base/trace_event/memory_dump_manager.h
@@ -238,6 +238,9 @@ class BASE_EXPORT MemoryDumpManager : public TraceLog::EnabledStateObserver {
     // Callback passed to the initial call to CreateProcessDump().
     MemoryDumpCallback callback;
 
+    // The |success| field that will be passed as argument to the |callback|.
+    bool dump_successful;
+
     // The thread on which FinalizeDumpAndAddToTrace() (and hence |callback|)
     // should be invoked. This is the thread on which the initial
     // CreateProcessDump() request was called.