[Smart Lock] Add a setting to require close proximity in order for unlocking to work.

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 3b55164eea31eee2a3a78e41ce150602c3634bb2..6247c4787ba20e9a9bf151f47d4848f4b8517c80 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -28,6 +28,7 @@
 #include "components/cloud_devices/common/cloud_devices_switches.h"
 #include "components/metrics/metrics_hashes.h"
 #include "components/nacl/common/nacl_switches.h"
+#include "components/proximity_auth/switches.h"
 #include "components/search/search_switches.h"
 #include "content/public/browser/user_metrics.h"
 #include "media/base/media_switches.h"
@@ -928,6 +929,13 @@ const Experiment kExperiments[] = {
     kOsCrOSOwnerOnly,
     SINGLE_VALUE_TYPE(chromeos::switches::kDisableEasySignin),
   },
+  {
+    "enable-easy-unlock-proximity-detection",
+    IDS_FLAGS_ENABLE_EASY_UNLOCK_PROXIMITY_DETECTION_NAME,
+    IDS_FLAGS_ENABLE_EASY_UNLOCK_PROXIMITY_DETECTION_DESCRIPTION,
+    kOsCrOS,
+    SINGLE_VALUE_TYPE(proximity_auth::switches::kEnableProximityDetection)
+  },
 #endif
 #if defined(USE_ASH)
   {
@@ -2010,7 +2018,7 @@ const Experiment kExperiments[] = {
     IDS_FLAGS_DISABLE_NEW_ZIP_UNPACKER_DESCRIPTION,
     kOsCrOS,
     SINGLE_VALUE_TYPE(chromeos::switches::kDisableNewZIPUnpacker)
-  }
+  },
 #endif  // defined(OS_CHROMEOS)
   // NOTE: Adding new command-line switches requires adding corresponding
   // entries to enum "LoginCustomFlags" in histograms.xml. See note in