libmix: use surfaceWidth/surfaceHeight to reflect the buffer size allocated by gralloc

BZ: 145977

720p surface buffers are always allocated in webrtc, in this scene, vaCreateSurfaces
need accecpt surfaceWidth/surfaceHeight as the buffer size allocated by gralloc.

Change-Id: I50cc6f5026c2f36b7659980955377ec20aa37974
Signed-off-by: Gu, Wangyi <wangyi.gu@intel.com>
diff --git a/videodecoder/VideoDecoderBase.cpp b/videodecoder/VideoDecoderBase.cpp
index 7f04e3d..c67ed7c 100755
--- a/videodecoder/VideoDecoderBase.cpp
+++ b/videodecoder/VideoDecoderBase.cpp
@@ -852,8 +852,8 @@
         vaStatus = vaCreateSurfaces(
             mVADisplay,
             format,
-            mVideoFormatInfo.width,
-            mVideoFormatInfo.height,
+            mVideoFormatInfo.surfaceWidth,
+            mVideoFormatInfo.surfaceHeight,
             mSurfaces,
             mNumSurfaces,
             attribs,