Add new telecom metrics for emergency dialer

These includes,
1. The source where user initiated the call.
2. The duration between START_CONNECTION and REQUEST_DISCONNECT.

Bug: 111818008
Test: manual and check the result of
'adb shell dumpsys telecom' for metrics data
Change-Id: Iddc7f256362abe9fe252bd12cead05a7d77d329e
diff --git a/telecomm/java/android/telecom/TelecomManager.java b/telecomm/java/android/telecom/TelecomManager.java
index 48c1e24..4e22823 100644
--- a/telecomm/java/android/telecom/TelecomManager.java
+++ b/telecomm/java/android/telecom/TelecomManager.java
@@ -622,6 +622,18 @@
             "android.telecom.extra.USE_ASSISTED_DIALING";
 
     /**
+     * Optional extra for {@link #placeCall(Uri, Bundle)} containing an integer that specifies
+     * the source where user initiated this call. This data is used in metrics.
+     * Valid source are:
+     * {@link ParcelableCallAnalytics#CALL_SOURCE_UNSPECIFIED},
+     * {@link ParcelableCallAnalytics#CALL_SOURCE_EMERGENCY_DIALPAD},
+     * {@link ParcelableCallAnalytics#CALL_SOURCE_EMERGENCY_SHORTCUT}.
+     *
+     * @hide
+     */
+    public static final String EXTRA_CALL_SOURCE = "android.telecom.extra.CALL_SOURCE";
+
+    /**
      * The following 4 constants define how properties such as phone numbers and names are
      * displayed to the user.
      */