Auto-play ads in same-video usecase.

Resume on contentcanplay.
We now auto-play when an ad gets loaded if we're playing ads in the same video element as the content.
The problem is that in IE11, we cannot play in addurationchange but in iOS8, we cannot play from adcanplay.
This will allow ad-integrations from needing to do this themselves.

src/videojs.ads.js

@@ -316,7 +316,7 @@ var
       // safari requires a call to `load` to pick up a changed source
       player.load();
       // and then resume from the snapshots time once the original src has loaded
-      player.one('contentloadedmetadata', tryToResume);
+      player.one('contentcanplay', tryToResume);
     } else if (!player.ended() || !snapshot.ended) {
       // if we didn't change the src, just restore the tracks
       restoreTracks();
@@ -430,6 +430,18 @@ var
       return redispatch;
     })();
 
+    // We now auto-play when an ad gets loaded if we're playing ads in the same video element as the content.
+    // The problem is that in IE11, we cannot play in addurationchange but in iOS8, we cannot play from adcanplay.
+    // This will allow ad-integrations from needing to do this themselves.
+    player.on(['addurationchange', 'adcanplay'], function(event) {
+      var snapshot = player.ads.snapshot;
+      if (player.currentSrc() === snapshot.src) {
+        return;  // do nothing
+      }
+
+      player.play();
+    });
+
     // replace the ad initializer with the ad namespace
     player.ads = {
       state: 'content-set',