cros: Add a header for gaia auth requests.

chrome/browser/resources/gaia_auth/background.js

+/**
+ * OnBeforeSendHeaders handler for sub frame requests. It adds a http header
+ * to all requests to indicate that they originate from this extension.
+ * @param {!Object} details Object contains detailed request info.
+ * @return {!Object} A BlockingResponse object with modified headers.
+ */
+var handleBeforeSendHeadersForSubFrame = function(details) {
+  details.requestHeaders.push({
+    name: 'X-Origin',
+    value: 'CrOS-Auth-Ext'
+  });
+  return {requestHeaders: details.requestHeaders};
+};
+
+chrome.webRequest.onBeforeSendHeaders.addListener(
+    handleBeforeSendHeadersForSubFrame,
+    {
+      urls: ['<all_urls>'],
+      types: ['sub_frame']
+    },
+    ['blocking', 'requestHeaders']);