Revert "Allow back to be pressed while in incoming call screen"

This reverts commit bd9ccd501ebd83508dfe52121e0f4827cc6e1fa3.

Bug: 18742942
Change-Id: I8016ddae8addb56b4d6350748628fec351e6531a
diff --git a/src/com/android/incallui/InCallActivity.java b/src/com/android/incallui/InCallActivity.java
index 0069364..6f48a35 100644
--- a/src/com/android/incallui/InCallActivity.java
+++ b/src/com/android/incallui/InCallActivity.java
@@ -330,6 +330,13 @@
             return;
         }
 
+        // Always disable the Back key while an incoming call is ringing
+        final Call call = CallList.getInstance().getIncomingCall();
+        if (call != null) {
+            Log.d(this, "Consume Back press for an incoming call");
+            return;
+        }
+
         // Nothing special to do.  Fall back to the default behavior.
         super.onBackPressed();
     }