Have Walker Surface Error

When the walker encounters an error, it handles the error but it did not
surface the error. This made it hard to log the error without putting
the log statement in the walker.

This changes the walker to pass the error to the handle error method so
that the class using the player (e.g. Player) can use the error in
determining how to respond to the error.

Change-Id: Ied91f8fcf80d5dd8058e8ba58de16d25213c2f0b

lib/player.js

@@ -269,7 +269,15 @@ shaka.Player = function(mediaElement, dependencyInjector) {
       const action = actions.get(node);
       return action(has, wants);
     },
-    handleError: async (has) => {
+    handleError: async (has, error) => {
+      shaka.log.warning('The walker saw an error:');
+      if (error instanceof shaka.util.Error) {
+        shaka.log.warning('Error Code:', error.code);
+      } else {
+        shaka.log.warning('Error Message:', error.message);
+        shaka.log.warning('Error Stack:', error.stack);
+      }
+
       // TODO(vaage): We don't always need to return to detached. If we have a
       //              video element we may want to return to attached. We should
       //              have this so that we return to |attachNode| when

lib/routing/walker.js

@@ -370,7 +370,8 @@ shaka.routing.Walker = class {
       // Still need to handle error because aborting an operation could leave us
       // in an unexpected state.
       this.currentlyAt_ = await this.implementation_.handleError(
-          this.currentlyWith_);
+          this.currentlyWith_,
+          error);
     }
   }
 
@@ -400,7 +401,8 @@ shaka.routing.Walker = class {
  *       shaka.routing.Payload,
  *       shaka.routing.Payload):!shaka.util.AbortableOperation,
  *   handleError: function(
- *       shaka.routing.Payload):!Promise.<shaka.routing.Node>
+ *       shaka.routing.Payload,
+ *       !Error):!Promise.<shaka.routing.Node>
  * }}
  *
  * @description
@@ -427,11 +429,13 @@ shaka.routing.Walker = class {
  *   payload.
  *
  * @property {function(
- *     shaka.routing.Payload):!Promise.<shaka.routing.Node> handleError
- *   When |enterNode| throws an error or is aborted, this will be called. This
- *   allows the walker to reset to a usable state. This method will be passed
- *   the current payload and will return the node that the walker starts at.
- *   This method may modify the current payload.
+ *     shaka.routing.Payload,
+ *     !Error):!Promise.<shaka.routing.Node> handleError
+ *   This is the callback for when |enterNode| fails. It is passed the current
+ *   payload and the error. If a step is aborted, the error will be
+ *   OPERATION_ABORTED. It should reset all external dependences, modify the
+ *   payload, and return the new current node. Calls to |handleError| should
+ *   always resolve and the walker should always be able to continue operating.
  */
 shaka.routing.Walker.Implementation;