cros/video: Update histogram naming for Arc's VDA.

The name was updated in https://codereview.chromium.org/2919193002/.

BUG=chromium:732192
TEST=Run the test on ChromeOS device with ARC.
CQ-DEPEND=CL:*392288

Change-Id: I996ace383fa65389a50701577c30becac2b82a3d
Reviewed-on: https://chromium-review.googlesource.com/530428
Commit-Ready: Owen Lin <owenlin@chromium.org>
Tested-by: Owen Lin <owenlin@chromium.org>
Reviewed-by: Pawel Osciak <posciak@chromium.org>
diff --git a/client/cros/video/constants.py b/client/cros/video/constants.py
index ad589ef..557ae6a 100644
--- a/client/cros/video/constants.py
+++ b/client/cros/video/constants.py
@@ -28,8 +28,9 @@
 RTC_INIT_HISTOGRAM = 'Media.RTCVideoDecoderInitDecodeSuccess'
 MEDIA_GVD_BUCKET = 0
 RTC_VIDEO_INIT_BUCKET = 1
-MEDIA_AGVDA_INIT_STATUS = 'Media.ArcGpuVideoDecodeAccelerator.InitializeResult'
-MEDIA_AGVDA_BUCKET = 0
+MEDIA_CAVDA_INIT_STATUS = (
+    'Media.ChromeArcVideoDecodeAccelerator.InitializeResult')
+MEDIA_CAVDA_BUCKET = 0
 
 #Path for video HTML file which helps for video operations
 CROS_VIDEO_DIR = '/usr/local/autotest/cros/video'