Remove atomicops.h from WebRTC

atomicops.h are not necessary in trace_event.h similar to the port in WebKit.
It will cause a benign race condition detected by TSAN. If it shows up in
TSAN we will either suppress it or annotate it with dynamic annotations.

BUG=1215
Review URL: https://webrtc-codereview.appspot.com/982004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@3267 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/system_wrappers/interface/trace_event.h b/webrtc/system_wrappers/interface/trace_event.h
index fd581a4..eecf4f6 100644
--- a/webrtc/system_wrappers/interface/trace_event.h
+++ b/webrtc/system_wrappers/interface/trace_event.h
@@ -8,7 +8,6 @@
 
 #include <string>
 
-#include "webrtc/system_wrappers/interface/atomicops.h"
 #include "webrtc/system_wrappers/interface/event_tracer.h"
 
 #if defined(TRACE_EVENT0)
@@ -595,21 +594,11 @@
     INTERNAL_TRACE_EVENT_UID2(name_prefix, __LINE__)
 
 // Implementation detail: internal macro to create static category.
-// No barriers are needed, because this code is designed to operate safely
-// even when the unsigned char* points to garbage data (which may be the case
-// on processors without cache coherency).
 #define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category) \
-    static webrtc::subtle::AtomicWord INTERNAL_TRACE_EVENT_UID(atomic) = 0; \
-    const uint8_t* INTERNAL_TRACE_EVENT_UID(catstatic) = \
-        reinterpret_cast<const uint8_t*>( \
-            webrtc::subtle::NoBarrier_Load( \
-                &INTERNAL_TRACE_EVENT_UID(atomic))); \
+    static const unsigned char* INTERNAL_TRACE_EVENT_UID(catstatic) = 0; \
     if (!INTERNAL_TRACE_EVENT_UID(catstatic)) { \
       INTERNAL_TRACE_EVENT_UID(catstatic) = \
           TRACE_EVENT_API_GET_CATEGORY_ENABLED(category); \
-      webrtc::subtle::NoBarrier_Store(&INTERNAL_TRACE_EVENT_UID(atomic), \
-          reinterpret_cast<webrtc::subtle::AtomicWord>( \
-              INTERNAL_TRACE_EVENT_UID(catstatic))); \
     }
 
 // Implementation detail: internal macro to create static category and add