Move unlimitedStorage permission from //chrome to //extensions

APIPermission::kUnlimitedStorage is used in the storage implementation in
//extensions so the permission should live there.

This allows app_shell to load apps with unlimitedStorage in the manifest.

BUG=none
TEST=existing browser_tests

Review URL: https://codereview.chromium.org/805563002

Cr-Commit-Position: refs/heads/master@{#308229}

chrome/common/extensions/api/_permission_features.json

@@ -1001,12 +1001,6 @@
     "channel": "stable",
     "extension_types": ["extension", "legacy_packaged_app"]
   },
-  "unlimitedStorage": {
-    "channel": "stable",
-    "extension_types": [
-      "extension", "legacy_packaged_app", "hosted_app", "platform_app"
-    ]
-  },
   "virtualKeyboardPrivate": {
     "channel": "stable",
     "extension_types": ["extension"],

extensions/common/api/_permission_features.json

@@ -271,6 +271,12 @@
       "whitelist": ["B44D08FD98F1523ED5837D78D0A606EA9D6206E5"]  // Web Store
     }
   ],
+  "unlimitedStorage": {
+    "channel": "stable",
+    "extension_types": [
+      "extension", "legacy_packaged_app", "hosted_app", "platform_app"
+    ]
+  },
   "usb": [
     {
       "channel": "stable",