Support conference calling. (2/4)

Bug: 15006702
Change-Id: I2764ea242f783ba478c9eae86618dd33e9fc792a
diff --git a/src/com/android/telecomm/CallIdMapper.java b/src/com/android/telecomm/CallIdMapper.java
index 7f92067..e6b5c1f 100644
--- a/src/com/android/telecomm/CallIdMapper.java
+++ b/src/com/android/telecomm/CallIdMapper.java
@@ -38,12 +38,15 @@
         mCalls.put(callId, newCall);
     }
 
+    void addCall(Call call, String id) {
+        Preconditions.checkNotNull(call);
+        ThreadUtil.checkOnMainThread();
+        mCalls.put(id, call);
+    }
+
     void addCall(Call call) {
         ThreadUtil.checkOnMainThread();
-        Preconditions.checkNotNull(call);
-        sIdCount++;
-        String callId = mCallIdPrefix + sIdCount;
-        mCalls.put(callId, call);
+        addCall(call, getNewId());
     }
 
     void removeCall(Call call) {
@@ -91,4 +94,9 @@
         // Note, no need for thread check, this method is thread safe.
         return callId != null && callId.startsWith(mCallIdPrefix);
     }
+
+    String getNewId() {
+        sIdCount++;
+        return mCallIdPrefix + sIdCount;
+    }
 }