[EasyUnlock] Add a private API for establishing an insecure Bluetooth connection.

This is needed to avoid a pairing request prompt when connecting to a service on
a system that tries to upgrade the connection from general bonding to general
bonding with MITM protection, which according to Android and ChromeOS Bluetooth
experts is the correct behavior.

BUG=403069
TEST=chrome.easyUnlockPrivate.connectToBluetoothServiceInsecurely() should work
     just like chrome.bluetoothSocket.connect(), but not show a pairing request
     prompt when pairing with Android L.
[email protected], [email protected]

Review URL: https://codereview.chromium.org/491753002

Cr-Commit-Position: refs/heads/master@{#291353}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@291353 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/extensions/browser/extension_function_histogram_value.h b/extensions/browser/extension_function_histogram_value.h
index 2663d1f..197d04e 100644
--- a/extensions/browser/extension_function_histogram_value.h
+++ b/extensions/browser/extension_function_histogram_value.h
@@ -942,6 +942,7 @@
   EASYUNLOCKPRIVATE_SETREMOTEDEVICES,
   EASYUNLOCKPRIVATE_GETREMOTEDEVICES,
   FILESYSTEMPROVIDER_GETALL,
+  EASYUNLOCKPRIVATE_CONNECTTOBLUETOOTHSERVICEINSECURELY,
   // Last entry: Add new entries above and ensure to update
   // tools/metrics/histograms/histograms.xml.
   ENUM_BOUNDARY