Add experimental location features to the about:flags page

Also update chromeactions.txt to record new UMAs

BUG=58277
TEST=enable, run browser with "--vmodule=*location*=3  http://html5demos.com/geo", check "gateways": appears in the log.

Review URL: http://codereview.chromium.org/5346009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@67838 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 44e18df..38ea7f7 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -255,6 +255,13 @@
     IDS_FLAGS_DISABLE_HYPERLINK_AUDITING_DESCRIPTION,
     kOsAll,
     switches::kNoPings
+  },
+  {
+    "experimental-location-features",  // FLAGS:RECORD_UMA
+    IDS_FLAGS_EXPERIMENTAL_LOCATION_FEATURES_NAME,
+    IDS_FLAGS_EXPERIMENTAL_LOCATION_FEATURES_DESCRIPTION,
+    kOsMac | kOsWin | kOsLinux,  // Currently does nothing on CrOS.
+    switches::kExperimentalLocationFeatures
   }
 };