Take ownership of device API flags

This change assigns owners for the following flags that are owned
by myself:

 * enable-generic-sensor (launched)
 * enable-generic-sensor-extra-classes
 * new-usb-backend

Bug: 897809
Change-Id: I7642770769398bb31035a18374b060a94f1b02cb
Reviewed-on: https://chromium-review.googlesource.com/c/1340955Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Reilly Grant <reillyg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609742}

chrome/browser/flag-metadata.json

@@ -1213,12 +1213,12 @@
   },
   {
     "name": "enable-generic-sensor",
-    // "owners": [ "your-team" ],
-    "expiry_milestone": 76
+    "owners": [ "reillyg@chromium.org", "raphael.kubo.da.costa@intel.com" ],
+    "expiry_milestone": 72
   },
   {
     "name": "enable-generic-sensor-extra-classes",
-    // "owners": [ "your-team" ],
+    "owners": [ "reillyg@chromium.org", "raphael.kubo.da.costa@intel.com" ],
     "expiry_milestone": 76
   },
   {
@@ -2460,7 +2460,7 @@
   },
   {
     "name": "new-usb-backend",
-    // "owners": [ "your-team" ],
+    "owners": [ "reillyg@chromium.org" ],
     "expiry_milestone": 76
   },
   {