Move VideoFrame and related declarations to webrtc/api/video.

Moves webrtc/common_video/rotation.h and parts of
webrtc/common_video/include/video_frame_buffer.h and
webrtc/video_frame.h, and adds to a new GN target api:video_frame_api.

BUG=webrtc:5880

Review-Url: https://codereview.webrtc.org/2517173004
Cr-Commit-Position: refs/heads/master@{#15993}
diff --git a/webrtc/sdk/objc/Framework/Classes/RTCNativeNV12Shader.mm b/webrtc/sdk/objc/Framework/Classes/RTCNativeNV12Shader.mm
index 75a575b..5000dbc 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCNativeNV12Shader.mm
+++ b/webrtc/sdk/objc/Framework/Classes/RTCNativeNV12Shader.mm
@@ -19,9 +19,9 @@
 #import "RTCShader+Private.h"
 #import "WebRTC/RTCVideoFrame.h"
 
+#include "webrtc/api/video/video_rotation.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/base/optional.h"
-#include "webrtc/common_video/rotation.h"
 
 static const char kNV12FragmentShaderSource[] =
   SHADER_VERSION