fix(MediaCap): Default video width and height to 1

When querying MediaCapabilities.decodingInfo(), if the video width
or height is not present, set 1 as default. Linux Firefox would
claim the variant is unsupported via decodingInfo() if the values
are falsy.

Issue shaka-project#1391

Change-Id: Idc27e6869a1276585a0ca35bd380e1b7ad1db242

lib/util/stream_utils.js

@@ -364,8 +364,8 @@ shaka.util.StreamUtils = class {
       // VideoConfiguration
       mediaDecodingConfig['video'] = {
         contentType: fullType,
-        width: video.width || 0,
-        height: video.height || 0,
+        width: video.width || 1,
+        height: video.height || 1,
         bitrate: video.bandwidth || variant.bandwidth || 1,
         // framerate must be greater than 0, otherwise the config is invalid.
         framerate: video.frameRate || 1,