cricket::VideoFrame cleanup. New width() and height(). Deleted GetChroma* methods.

talk/app/webrtc/objc/RTCI420Frame.mm

Index: talk/app/webrtc/objc/RTCI420Frame.mm
diff --git a/talk/app/webrtc/objc/RTCI420Frame.mm b/talk/app/webrtc/objc/RTCI420Frame.mm
index d8be8ceed14e1aa85b2ca9e95e44ba00b0bea66f..3d9ef0427255c5c997a9104f09abda64588cc053 100644
--- a/talk/app/webrtc/objc/RTCI420Frame.mm
+++ b/talk/app/webrtc/objc/RTCI420Frame.mm
@@ -36,23 +36,22 @@
 }
 
 - (NSUInteger)width {
-  return _videoFrame->GetWidth();
+  return _videoFrame->width();
 }
 
 - (NSUInteger)height {
-  return _videoFrame->GetHeight();
+  return _videoFrame->height();
 }
 
+// TODO(nisse): chromaWidth and chromaHeight are used only in
+// RTCOpenGLVideoRenderer.mm. Update, and then delete these
+// properties.
 - (NSUInteger)chromaWidth {
-  return _videoFrame->GetChromaWidth();
+  return (self.width + 1) / 2;
 }
 
 - (NSUInteger)chromaHeight {
-  return _videoFrame->GetChromaHeight();
-}
-
-- (NSUInteger)chromaSize {
-  return _videoFrame->GetChromaSize();
+  return (self.height + 1) / 2;
 }
 
 - (const uint8_t*)yPlane {