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

This reverts commit ad84e0637f.

Bug: 18742942
Change-Id: I6c0a1651526a37cca8e27be9fbd36a2f59943366

policy/src/com/android/internal/policy/impl/PhoneWindowManager.java

@@ -2208,6 +2208,15 @@ public class PhoneWindowManager implements WindowManagerPolicy {
                     return -1;
                 }
 
+                // If an incoming call is ringing, HOME is totally disabled.
+                // (The user is already on the InCallUI at this point,
+                // and his ONLY options are to answer or reject the call.)
+                TelecomManager telecomManager = getTelecommService();
+                if (telecomManager != null && telecomManager.isRinging()) {
+                    Log.i(TAG, "Ignoring HOME; there's a ringing incoming call.");
+                    return -1;
+                }
+
                 // Delay handling home if a double-tap is possible.
                 if (mDoubleTapOnHomeBehavior != DOUBLE_TAP_HOME_NOTHING) {
                     mHandler.removeCallbacks(mHomeDoubleTapTimeoutRunnable); // just in case