Move CoreVideoFrameBuffer from webrtc/common_video/ to webrtc/sdk/objc/

CoreVideoFrameBuffer is Mac/iPhone specific and should be moved into
the webrtc/sdk/objc/ folder.

BUG=None

Review-Url: https://codereview.webrtc.org/2851563003
Cr-Commit-Position: refs/heads/master@{#17998}

webrtc/sdk/objc/Framework/Classes/avfoundationvideocapturer.mm

@@ -23,7 +23,7 @@
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/base/thread.h"
-#include "webrtc/common_video/include/corevideo_frame_buffer.h"
+#include "webrtc/sdk/objc/Framework/Classes/corevideo_frame_buffer.h"
 
 namespace webrtc {