Fix event tracing for windows test flakyness....

base/event_trace_controller_win.cc

Index: base/event_trace_controller_win.cc
===================================================================
--- base/event_trace_controller_win.cc	(revision 62730)
+++ base/event_trace_controller_win.cc	(working copy)
@@ -97,6 +97,7 @@
 
 HRESULT EtwTraceController::Start(const wchar_t* session_name,
     EtwTraceProperties* properties, TRACEHANDLE* session_handle) {
+  DCHECK(properties != NULL);
   ULONG err = ::StartTrace(session_handle, session_name, properties->get());
   return HRESULT_FROM_WIN32(err);
 }
@@ -110,6 +111,7 @@
 
 HRESULT EtwTraceController::Update(const wchar_t* session_name,
     EtwTraceProperties* properties) {
+  DCHECK(properties != NULL);
   ULONG err = ::ControlTrace(NULL, session_name, properties->get(),
                              EVENT_TRACE_CONTROL_UPDATE);
   return HRESULT_FROM_WIN32(err);
@@ -117,6 +119,7 @@
 
 HRESULT EtwTraceController::Stop(const wchar_t* session_name,
     EtwTraceProperties* properties) {
+  DCHECK(properties != NULL);
   ULONG err = ::ControlTrace(NULL, session_name, properties->get(),
                              EVENT_TRACE_CONTROL_STOP);
   return HRESULT_FROM_WIN32(err);
@@ -124,6 +127,7 @@
 
 HRESULT EtwTraceController::Flush(const wchar_t* session_name,
     EtwTraceProperties* properties) {
+  DCHECK(properties != NULL);
   ULONG err = ::ControlTrace(NULL, session_name, properties->get(),
                              EVENT_TRACE_CONTROL_FLUSH);
   return HRESULT_FROM_WIN32(err);