Add loginState permission to chromecast extension features/permissions

This API is requested by the chromevox extension manifest but not
used in chromecast.  This causes a DCHECK failure in the manifest
permissions parser.  Adding the feature/permission here so DCHECK
doesn't cause failure to install the extension in eng builds.

Test: Local build with x86 chromecast simulator (eng)
Bug: None
Change-Id: I9ceb769b768f15ab523653afe3defc7f1627d9a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2007477Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Commit-Queue: Randy Rossi <rmrossi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#733447}

chromecast/common/extensions_api/_api_features.json

@@ -113,6 +113,10 @@
     "dependencies": ["permission:tts"],
     "contexts": ["blessed_extension"]
   },
+  "loginState": {
+    "dependencies": ["permission:loginState"],
+    "contexts": ["blessed_extension"]
+  },
   "windows": [{
     "dependencies": ["api:tabs"],
     "contexts": ["blessed_extension"]

chromecast/common/extensions_api/_permission_features.json

@@ -72,5 +72,9 @@
   "tabs": {
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"]
+  },
+  "loginState": {
+    "channel": "stable",
+    "extension_types": ["extension"]
   }
 }