Expand usage of platform-apps flag and permission features.

chrome/common/extensions/api/_permission_features.json

Index: chrome/common/extensions/api/_permission_features.json
diff --git a/chrome/common/extensions/api/_permission_features.json b/chrome/common/extensions/api/_permission_features.json
index 425f59ec1db31bc145d636366660cee5dc0c04c8..f9dd6474fc31cab5f806ee63581492ead3f50e22 100644
--- a/chrome/common/extensions/api/_permission_features.json
+++ b/chrome/common/extensions/api/_permission_features.json
@@ -59,6 +59,9 @@
   "devtools": {
     "extension_types": ["extension", "packaged_app", "platform_app"]
   },
+  "dns": {
+    "extension_types": ["platform_app"]
+  },
   "experimental": {
     "extension_types": [
       "extension", "packaged_app", "hosted_app", "platform_app"
@@ -79,6 +82,9 @@
   "history": {
     "extension_types": ["extension", "packaged_app", "platform_app"]
   },
+  "identity": {
+    "extension_types": ["platform_app"]
+  },
   "idle": {
     "extension_types": ["extension", "packaged_app", "platform_app"]
   },
@@ -134,6 +140,9 @@
   "proxy": {
     "extension_types": ["extension", "packaged_app", "platform_app"]
   },
+  "serial": {
+    "extension_types": ["platform_app"]
+  },
   "socket": {
     "extension_types": ["platform_app"]
   },