Revert "Remove localhost from Hangouts services extension manifest."

This reverts commit 13dc6be4.

Reason for revert: Broke official Chrome builder.

Original change's description:
> Remove localhost from Hangouts services extension manifest.
> 
> Bug: 819406
> Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
> Change-Id: I9ec4028146c3a561f847a649848c5c16dde6e2a8
> Reviewed-on: https://chromium-review.googlesource.com/951684
> Reviewed-by: Patrik Höglund <phoglund@chromium.org>
> Commit-Queue: Henrik Grunell <grunell@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#544656}

TBR=grunell@chromium.org,phoglund@chromium.org,jansson@chromium.org

Change-Id: Id11dbe77e63a4ca73badce8efe959f601ccf4306
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 819406, 824632
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Reviewed-on: https://chromium-review.googlesource.com/974382Reviewed-by: Henrik Grunell <grunell@chromium.org>
Commit-Queue: Henrik Grunell <grunell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545007}

chrome/browser/resources/hangout_services/manifest.json

@@ -9,7 +9,9 @@
   "manifest_version": 2,
   "externally_connectable": {
     "matches": [
-      "https://*.google.com/*"
+      "https://*.google.com/*",
+      // For tests.
+      "*://localhost/*"
     ]
   },
   "background": {