Adding Mac test renderer, some test refactoring and made cpplint pass.

BUG=1667
TEST=Rendered video in Mac loopback test.
R=pbos@webrtc.org, xians@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/1554004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@4112 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/video_engine/test/common/video_renderer.h b/video_engine/test/common/video_renderer.h
index b312fbe..ef4168f 100644
--- a/video_engine/test/common/video_renderer.h
+++ b/video_engine/test/common/video_renderer.h
@@ -17,9 +17,17 @@
 
 class VideoRenderer : public newapi::VideoRenderer {
  public:
-  static VideoRenderer* Create(const char* window_title,
-                               size_t width,
+  // Creates a platform-specific renderer if possible, or a null implementation
+  // if failing.
+  static VideoRenderer* Create(const char* window_title, size_t width,
                                size_t height);
+  // Returns a renderer rendering to a platform specific window if possible,
+  // NULL if none can be created.
+  // Creates a platform-specific renderer if possible, returns NULL if a
+  // platform renderer could not be created. This occurs, for instance, when
+  // running without an X environment on Linux.
+  static VideoRenderer* CreatePlatformRenderer(const char* window_title,
+                                               size_t width, size_t height);
   virtual ~VideoRenderer() {}
  protected:
   VideoRenderer() {}