Retain current visibility when copying layoutparam

The LayoutParams members, systemUiVisibility and
subtreeSystemUiVisibility are derived values rather than app-generated
values. When copying LayoutParams members make sure these values are
not overwritten.

Overwriting them was causing the STATUS_BAR_DISABLE_XXX flags to be
overwritten exposing elements that should have remained hidden.

Fixes bug b6374541.

Change-Id: Iaae4b4167e1b148bbdba4d05f473844f7fa3bf8d

Author: Craig Mautner

core/java/android/view/ViewRootImpl.java

@@ -763,6 +763,9 @@ void setLayoutParams(WindowManager.LayoutParams attrs, boolean newView) {
             // preserve compatible window flag if exists.
             int compatibleWindowFlag =
                 mWindowAttributes.flags & WindowManager.LayoutParams.FLAG_COMPATIBLE_WINDOW;
+            // transfer over system UI visibility values as they carry current state.
+            attrs.systemUiVisibility = mWindowAttributes.systemUiVisibility;
+            attrs.subtreeSystemUiVisibility = mWindowAttributes.subtreeSystemUiVisibility;
             mWindowAttributesChangesFlag = mWindowAttributes.copyFrom(attrs);
             mWindowAttributes.flags |= compatibleWindowFlag;