Use visible frame instead of task bounds for detecting resize start

Initial task bounds might be adjusted (for status bar, etc.). Touch
should be set up using visible frames instead of task bounds.

bug: 24336351
Change-Id: I944e3185a06c39b451432bdda5ad87880a0482f3
diff --git a/services/core/java/com/android/server/wm/Task.java b/services/core/java/com/android/server/wm/Task.java
index 6ebff42..d1111f7 100644
--- a/services/core/java/com/android/server/wm/Task.java
+++ b/services/core/java/com/android/server/wm/Task.java
@@ -437,6 +437,11 @@
         return mStack != null && mStack.mStackId == DOCKED_STACK_ID;
     }
 
+    WindowState getTopAppMainWindow() {
+        final int tokensCount = mAppTokens.size();
+        return tokensCount > 0 ? mAppTokens.get(tokensCount - 1).findMainWindow() : null;
+    }
+
     @Override
     public boolean isFullscreen() {
         return mFullscreen;