Add extension permissions for Media Gallery API.

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 55e8e66e58c28c95a935f0afb7f5bd002dc5412a..526aee974823b8d43a5998a53f2655629bb6421c 100644
--- a/chrome/common/extensions/api/_permission_features.json
+++ b/chrome/common/extensions/api/_permission_features.json
@@ -175,6 +175,28 @@
     "channel": "stable",
     "extension_types": ["extension", "packaged_app"]
   },
+  "mediaGalleries": {
+    "channel": "dev",
+    "extension_types": [
+      "extension", "packaged_app", "hosted_app", "platform_app"
+    ]
+  },
+  "mediaGalleriesDefaultAll": {
+    "channel": "dev",
+    "extension_types": [ "platform_app" ]
+  },
+  "mediaGalleriesRead": {
+    "channel": "dev",
+    "extension_types": [
+      "extension", "packaged_app", "hosted_app", "platform_app"
+    ]
+  },
+  "mediaGalleriesWrite": {
+    "channel": "dev",
+    "extension_types": [
+      "extension", "packaged_app", "hosted_app", "platform_app"
+    ]
+  },
   "mediaPlayerPrivate": {
     "channel": "stable",
     "extension_types": ["extension", "packaged_app"],