Correct window replacement string comparison.

We were comparing the objects, not the strings, which happened
to work in many cases as they were both the same package name String.

Bug: 26668339
Change-Id: I025d05586cc6c11e788add967c7e6ad916cba276

services/core/java/com/android/server/wm/AppWindowToken.java

@@ -539,7 +539,7 @@ class AppWindowToken extends WindowToken {
         for (int i = allAppWindows.size() - 1; i >= 0; i--) {
             WindowState candidate = allAppWindows.get(i);
             if (candidate.mWillReplaceWindow && candidate.mReplacingWindow == null &&
-                    candidate.getWindowTag().equals(w.getWindowTag().toString())) {
+                    candidate.getWindowTag().toString().equals(w.getWindowTag().toString())) {
                 candidate.mReplacingWindow = w;
                 w.mSkipEnterAnimationForSeamlessReplacement = !candidate.mAnimateReplacingWindow;