Refactoring temporal layers implementation and adding VideoCodecMode for easier control of codec settings.

Review URL: https://webrtc-codereview.appspot.com/1105007

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@3528 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/common_types.h b/common_types.h
index 3c79137..58ac571 100644
--- a/common_types.h
+++ b/common_types.h
@@ -566,6 +566,11 @@
     unsigned int        qpMax; // minimum quality
 };
 
+enum VideoCodecMode {
+  kRealtimeVideo,
+  kScreensharing
+};
+
 // Common video codec properties
 struct VideoCodec
 {
@@ -586,6 +591,8 @@
     unsigned int        qpMax;
     unsigned char       numberOfSimulcastStreams;
     SimulcastStream     simulcastStream[kMaxSimulcastStreams];
+
+    VideoCodecMode      mode;
 };
 
 // Bandwidth over-use detector options.  These are used to drive