Merge "Fix issue #4974633: Block the HOME button using TYPE_KEYGUARD"

services/java/com/android/server/wm/WindowManagerService.java

@@ -2498,6 +2498,10 @@ public class WindowManagerService extends IWindowManager.Stub
             int attrChanges = 0;
             int flagChanges = 0;
             if (attrs != null) {
+                if (win.mAttrs.type != attrs.type) {
+                    throw new IllegalArgumentException(
+                            "Window type can not be changed after the window is added.");
+                }
                 flagChanges = win.mAttrs.flags ^= attrs.flags;
                 attrChanges = win.mAttrs.copyFrom(attrs);
             }