Add config for using src= on Safari.

Closes #2116.

Change-Id: I4742037563a20e2e585a6dfbeae29a65bffe2117

externs/shaka/player.js

@@ -639,7 +639,8 @@ shaka.extern.ManifestConfiguration;
  *   safeSeekOffset: number,
  *   stallEnabled: boolean,
  *   stallThreshold: number,
- *   stallSkip: number
+ *   stallSkip: number,
+ *   useNativeHlsOnSafari: boolean
  * }}
  *
  * @description
@@ -715,6 +716,11 @@ shaka.extern.ManifestConfiguration;
  * @property {number} stallSkip
  *   The number of seconds that the player will skip forward when a stall has
  *   been detected.
+ * @property {boolean} useNativeHlsOnSafari
+ *   Desktop Safari has both MediaSource and their native HLS implementation.
+ *   Depending on the application's needs, it may prefer one over the other.
+ *   Examples: FairPlay is only supported via Safari's native HLS, but it
+ *   doesn't have an API for selecting specific tracks.
  * @exportDoc
  */
 shaka.extern.StreamingConfiguration;

lib/player.js

@@ -1088,10 +1088,9 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
 
       // We would prefer MediaSource in some cases, and src= in others.  For
       // example, Android has native HLS, but we'd prefer our own MediaSource
-      // version there.  But for Safari desktop, we'd prefer the native one for
-      // now, because that's the only way we get FairPlay there.  So use src=
-      // over MSE on any Apple platform.
-      return Platform.isApple();
+      // version there.  For Safari, the choice is governed by the
+      // useNativeHlsOnSafari setting of the streaming config.
+      return Platform.isApple() && this.config_.streaming.useNativeHlsOnSafari;
     }
 
     // Unless there are good reasons to use src= (single-file playback or native

lib/util/platform.js

@@ -126,6 +126,7 @@ shaka.util.Platform = class {
            !shaka.util.Platform.isEdge();
   }
 
+
   /**
    * Check if the current platform is an Apple device (iOS, desktop Safari, etc)
    *

lib/util/player_configuration.js

@@ -131,6 +131,7 @@ shaka.util.PlayerConfiguration = class {
       stallEnabled: true,
       stallThreshold: 1 /* seconds */,
       stallSkip: 0.1 /* seconds */,
+      useNativeHlsOnSafari: true,
     };
 
     // WebOS has a long hardware pipeline that responds slowly, making it easy