Don't recurse on serverCertificate in config merge

Treating serverCertificate as an Object and recursing causes an
exception the second time you set the serverCertificate config.

As a quick fix that can be cherry-picked for v2.1.x, do not recurse
on serverCertificate.  This has the side-effect of not type-checking
the serverCertificate field on input.

A more detailed fix will be made later, for inclusion in v2.2.

Issue #784

Change-Id: I84c05ee3dd370a4b83e9ce2337d2326ec36532c2

lib/util/config_utils.js

@@ -51,7 +51,9 @@ shaka.util.ConfigUtils.mergeConfigObjects =
      */
     var copyObject = !!({
       '.abr.manager': true
-    })[subPath];
+    })[subPath] || !!({
+      'serverCertificate': true
+    })[k];
 
     // The order of these checks is important.
     if (!ignoreKeys && !(k in destination)) {

test/player_unit.js

@@ -642,6 +642,29 @@ describe('Player', function() {
       expect(newConfig.manifest.dash.customScheme).not.toBe(badCustomScheme2);
       expect(logWarnSpy).not.toHaveBeenCalled();
     });
+
+    // Regression test for https://github.com/google/shaka-player/issues/784
+    it('does not throw when overwriting serverCertificate', function() {
+      player.configure({
+        drm: {
+          advanced: {
+            'com.widevine.alpha': {
+              serverCertificate: new Uint8Array(1)
+            }
+          }
+        }
+      });
+
+      player.configure({
+        drm: {
+          advanced: {
+            'com.widevine.alpha': {
+              serverCertificate: new Uint8Array(2)
+            }
+          }
+        }
+      });
+    });
   });
 
   describe('AbrManager', function() {