Rename I420VideoFrame to VideoFrame.

This is a mechanical change since it affects so many
files.
I420VideoFrame -> VideoFrame
and reformatted.

Rationale: in the next CL I420VideoFrame will
get an indication of Pixel Format (I420 for
starters) and of storage type: usually
UNOWNED, could be SHMEM, and in the near
future will be possibly TEXTURE. See
https://codereview.chromium.org/1154153003
for the change that happened in Cr.

BUG=4730, chromium:440843
R=jiayl@webrtc.org, niklas.enbom@webrtc.org, pthatcher@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/52629004

Cr-Commit-Position: refs/heads/master@{#9339}
diff --git a/webrtc/test/frame_generator_unittest.cc b/webrtc/test/frame_generator_unittest.cc
index 7d9a3a4..6376e2c2 100644
--- a/webrtc/test/frame_generator_unittest.cc
+++ b/webrtc/test/frame_generator_unittest.cc
@@ -55,10 +55,7 @@
     fwrite(plane_buffer.get(), 1, uv_size, file);
   }
 
-  void CheckFrameAndMutate(I420VideoFrame* frame,
-                           uint8_t y,
-                           uint8_t u,
-                           uint8_t v) {
+  void CheckFrameAndMutate(VideoFrame* frame, uint8_t y, uint8_t u, uint8_t v) {
     // Check that frame is valid, has the correct color and timestamp are clean.
     ASSERT_NE(nullptr, frame);
     uint8_t* buffer;