libvpx's UNUSED macro conflicts with webrtc/base's. Added missing include of assert.h. Globally defined function "Unused" in talk/base and its copy (webrtc/base) is causing a conflict.

libvpx macro (UNUSED) can be found here:
http://src.chromium.org/viewvc/chrome/trunk/deps/third_party/libvpx/source/libvpx/vpx/vpx_codec.h

BUG=N/A
R=andrew@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/17489004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@6185 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/base/common.h b/base/common.h
index 51a5d1e..7f4a756 100644
--- a/base/common.h
+++ b/base/common.h
@@ -23,25 +23,24 @@
 // General Utilities
 //////////////////////////////////////////////////////////////////////
 
-// Note: UNUSED is also defined in basictypes.h
-#ifndef UNUSED
-#define UNUSED(x) Unused(static_cast<const void*>(&x))
-#define UNUSED2(x, y) Unused(static_cast<const void*>(&x)); \
-    Unused(static_cast<const void*>(&y))
-#define UNUSED3(x, y, z) Unused(static_cast<const void*>(&x)); \
-    Unused(static_cast<const void*>(&y)); \
-    Unused(static_cast<const void*>(&z))
-#define UNUSED4(x, y, z, a) Unused(static_cast<const void*>(&x)); \
-    Unused(static_cast<const void*>(&y)); \
-    Unused(static_cast<const void*>(&z)); \
-    Unused(static_cast<const void*>(&a))
-#define UNUSED5(x, y, z, a, b) Unused(static_cast<const void*>(&x)); \
-    Unused(static_cast<const void*>(&y)); \
-    Unused(static_cast<const void*>(&z)); \
-    Unused(static_cast<const void*>(&a)); \
-    Unused(static_cast<const void*>(&b))
-inline void Unused(const void*) {}
-#endif  // UNUSED
+#ifndef RTC_UNUSED
+#define RTC_UNUSED(x) RtcUnused(static_cast<const void*>(&x))
+#define RTC_UNUSED2(x, y) RtcUnused(static_cast<const void*>(&x)); \
+    RtcUnused(static_cast<const void*>(&y))
+#define RTC_UNUSED3(x, y, z) RtcUnused(static_cast<const void*>(&x)); \
+    RtcUnused(static_cast<const void*>(&y)); \
+    RtcUnused(static_cast<const void*>(&z))
+#define RTC_UNUSED4(x, y, z, a) RtcUnused(static_cast<const void*>(&x)); \
+    RtcUnused(static_cast<const void*>(&y)); \
+    RtcUnused(static_cast<const void*>(&z)); \
+    RtcUnused(static_cast<const void*>(&a))
+#define RTC_UNUSED5(x, y, z, a, b) RtcUnused(static_cast<const void*>(&x)); \
+    RtcUnused(static_cast<const void*>(&y)); \
+    RtcUnused(static_cast<const void*>(&z)); \
+    RtcUnused(static_cast<const void*>(&a)); \
+    RtcUnused(static_cast<const void*>(&b))
+inline void RtcUnused(const void*) {}
+#endif  // RTC_UNUSED
 
 #if !defined(WEBRTC_WIN)