Include viewport visibility checks for autoplay experiment.

LayoutTests/media/video-autoplay-experiment-modes-expected.txt

 CONSOLE WARNING: Failed to execute 'play' on 'HTMLMediaElement': API can only be initiated by a user gesture.
 CONSOLE WARNING: Failed to execute 'play' on 'HTMLMediaElement': API can only be initiated by a user gesture.
 CONSOLE WARNING: Failed to execute 'play' on 'HTMLMediaElement': API can only be initiated by a user gesture.
 CONSOLE WARNING: Failed to execute 'play' on 'HTMLMediaElement': API can only be initiated by a user gesture.
 CONSOLE WARNING: Failed to execute 'play' on 'HTMLMediaElement': API can only be initiated by a user gesture.
 CONSOLE WARNING: Failed to execute 'play' on 'HTMLMediaElement': API can only be initiated by a user gesture.
 CONSOLE WARNING: Failed to execute 'play' on 'HTMLMediaElement': API can only be initiated by a user gesture.
-CONSOLE WARNING: Failed to execute 'play' on 'HTMLMediaElement': API can only be initiated by a user gesture.
 END OF TEST
   Check if the autoplay gesture override experiment works.  There are a lot
   of config options, so this test just runs all of them.
 
   The "results" table contains one row per config tested.
   == Test Inputs ==
   #      - config number, in case you'd like to run just one.
   Flags  - autoplay experiment setting being tested.
                a      - "foraudio"
                v      - "forvideo"
+               V      - "ifviewport"
                M      - "ifmuted"
                p      - "playmuted"
                m      - "ifmobile"
-               For example, EM means "enabled-ifmuted".
+               For example, vM means '-forvideo-ifmuted".
   Type   - audio or video element?
                audio  - 
-#       Flags   Type    Play w/ Mute    Mobile  Played? Muted?
-0               video   none    no      no      no      -
-1               audio   none    no      no      no      -
-2       v       video   none    no      no      no      -
-3       v       audio   none    no      no      no      -
-4       vM      video   none    no      no      no      -
-5       vM      audio   none    no      no      no      -
-6       vp      video   none    no      no      no      -
-7       vp      audio   none    no      no      no      -
-8       a       video   none    no      no      no      -
-9       a       audio   none    no      no      no      -
-12              video   attr    no      no      no      -
-13              audio   attr    no      no      no      -
-14      v       video   attr    no      no      played  unmuted
-15      v       audio   attr    no      no      no      -
-16      vM      video   attr    no      no      no      -
-17      vM      audio   attr    no      no      no      -
-18      vp      video   attr    no      no      played  muted
-19      vp      audio   attr    no      no      no      -
-20      a       video   attr    no      no      no      -
-21      a       audio   attr    no      no      played  unmuted
-22      vm      video   attr    no      no      no      -
-24              video   play()  no      no      no      -
-25              audio   play()  no      no      no      -
-26      v       video   play()  no      no      played  unmuted
-27      v       audio   play()  no      no      no      -
-28      vM      video   play()  no      no      no      -
-29      vM      audio   play()  no      no      no      -
-30      vp      video   play()  no      no      played  muted
-31      vp      audio   play()  no      no      no      -
-32      a       video   play()  no      no      no      -
-33      a       audio   play()  no      no      played  unmuted
-40      vM      video   none    yes     no      no      -
-41      vM      audio   none    yes     no      no      -
-52      vM      video   attr    yes     no      played  muted
-53      vM      audio   attr    yes     no      no      -
-64      vM      video   play()  yes     no      played  muted
-65      vM      audio   play()  yes     no      no      -
-86      v       video   attr    no      yes     played  unmuted
-94      vm      video   attr    no      yes     played  unmuted
+#       Flags   Type    Play w/ Mute    Mobile  View    Early?  Played? Muted?
+0               video   none    no      no      onscree -       no      -
+2       v       video   none    no      no      onscree -       no      -
+4       vV      video   none    no      no      onscree -       no      -
+6       vVM     video   none    no      no      onscree -       no      -
+8       vVp     video   none    no      no      onscree -       no      -
+16              video   attr    no      no      onscree -       no      -
+18      v       video   attr    no      no      onscree -       played  unmuted
+20      vV      video   attr    no      no      onscree -       played  unmuted
+22      vVM     video   attr    no      no      onscree -       no      -
+24      vVp     video   attr    no      no      onscree -       played  muted
+26      a       video   attr    no      no      onscree -       no      -
+28      vm      video   attr    no      no      onscree -       no      -
+30      aV      video   attr    no      no      onscree -       no      -
+32              video   play()  no      no      onscree -       no      -
+34      v       video   play()  no      no      onscree -       played  unmuted
+36      vV      video   play()  no      no      onscree -       played  unmuted
+38      vVM     video   play()  no      no      onscree -       no      -
+40      vVp     video   play()  no      no      onscree -       played  muted
+54      vVM     video   none    yes     no      onscree -       no      -
+70      vVM     video   attr    yes     no      onscree -       played  muted
+86      vVM     video   play()  yes     no      onscree -       played  muted
+112             video   attr    no      no      scroll  no      no      -
+113             audio   attr    no      no      scroll  no      no      -
+114     v       video   attr    no      no      scroll  yes     played  unmuted
+116     vV      video   attr    no      no      scroll  no      played  unmuted
+120     vVp     video   attr    no      no      scroll  no      played  muted
+123     a       audio   attr    no      no      scroll  yes     played  unmuted
+127     aV      audio   attr    no      no      scroll  no      played  unmuted
+128             video   play()  no      no      scroll  no      no      -
+129             audio   play()  no      no      scroll  no      no      -
+130     v       video   play()  no      no      scroll  yes     played  unmuted
+132     vV      video   play()  no      no      scroll  no      played  unmuted
+136     vVp     video   play()  no      no      scroll  no      played  muted
+139     a       audio   play()  no      no      scroll  yes     played  unmuted
+143     aV      audio   play()  no      no      scroll  no      played  unmuted
+208             video   attr    no      no      offscre -       no      -
+210     v       video   attr    no      no      offscre -       played  unmuted
+212     vV      video   attr    no      no      offscre -       no      -
+216     vVp     video   attr    no      no      offscre -       no      -
+306     v       video   attr    no      yes     onscree -       played  unmuted
+316     vm      video   attr    no      yes     onscree -       played  unmuted
+