Fix "defined but not used" build error when enable_webrtc=false.

chrome/browser/renderer_preferences_util.cc

Index: chrome/browser/renderer_preferences_util.cc
diff --git a/chrome/browser/renderer_preferences_util.cc b/chrome/browser/renderer_preferences_util.cc
index ad5e3017221badabb2f640eebbfa41df4326b7db..aa4f1c212d2f7e9270239b3d553ad439e1af4a1d 100644
--- a/chrome/browser/renderer_preferences_util.cc
+++ b/chrome/browser/renderer_preferences_util.cc
@@ -36,6 +36,7 @@
 #include "ui/views/linux_ui/linux_ui.h"
 #endif
 
+#if defined(ENABLE_WEBRTC)
 namespace {
 
 // Parses a string |range| with a port range in the form "<min>-<max>".
@@ -75,6 +76,7 @@ void ParsePortRange(const std::string& range,
 }
 
 }  // namespace
+#endif
 
 namespace renderer_preferences_util {