Merge "Remove overzealous mutate() sanity check in LayerDrawable" into jb-mr1.1-dev

    @Override

    public Drawable mutate() {

        if (!mMutated && super.mutate() == this) {

            if (!mLayerState.canConstantState()) {

                throw new IllegalStateException("One or more children of this LayerDrawable does " +

                        "not have constant state; this drawable cannot be mutated.");

            }

            mLayerState = new LayerState(mLayerState, this, null);

            final ChildDrawable[] array = mLayerState.mChildren;

            final int N = mLayerState.mNum;