Enable WEBRTC_NO_TRACE for Chromium builds.

I'm also fixing WEBRTC_TRACE so that it won't break the build but on Linux I had to do something non traditional as is explained in the comments.
Review URL: http://webrtc-codereview.appspot.com/269012

git-svn-id: http://webrtc.googlecode.com/svn/trunk@939 4adac7df-926f-26a2-2b94-8c16560cd09d

src/build/common.gypi

@@ -95,6 +95,14 @@
       '..','../..', # common_types.h, typedefs.h
     ],
     'conditions': [
+      ['build_with_chromium==1', {
+        'defines': [
+          # This turns off tracing in webrtc to reduce the noise from
+          # the Chrome memory bots. Down the line we will enable WebRTC
+          # tracing for Chromium and remove this.
+          'WEBRTC_NO_TRACE',
+         ],
+      }],
       ['OS=="linux"', {
         'defines': [
           'WEBRTC_TARGET_PC',

src/system_wrappers/interface/trace.h

@@ -19,12 +19,24 @@
 #include "typedefs.h"
 
 #ifdef WEBRTC_NO_TRACE
-    #define WEBRTC_TRACE
+#ifdef WIN32
+   // Use __noop to avoid the C4353 compiler warning on Windows.
+   #define WEBRTC_TRACE  __noop()
 #else
-    // Ideally we would use __VA_ARGS__ but it's not supported by all compilers
-    // such as VS2003 (it's supported in VS2005). TODO (hellner) why
-    // would this be better than current implementation (not convinced)?
-    #define WEBRTC_TRACE Trace::Add
+   // This is a workaround.  Ideally we should be able to do
+   // something like:
+   // #define WEBRTC_TRACE(...)  ((void)0)
+   // However, we have code that creates variables with the only
+   // intent of tracing out their value.  So, if we take the above
+   // approach, then we'll get a compiler error about unused variables. :(
+   inline void WebRtcNoTrace(...) {}
+   #define WEBRTC_TRACE WebRtcNoTrace
+#endif
+#else
+   // Ideally we would use _VA_ARGS_ but it's not supported by all compilers
+   // such as VS2003 (it's supported in VS2005). TODO (hellner) why
+   // would this be better than current implementation (not convinced)?
+   #define WEBRTC_TRACE Trace::Add
 #endif
 
 namespace webrtc {