Merge "Clear native shader when Paint shader changes" into oc-dev

        // old shader's pointer may be reused by another shader allocation later

        if (mShader != shader) {

            mNativeShader = -1;

            // Release any native references to the old shader content

            nSetShader(mNativePaint, 0);

        }

        // Defer setting the shader natively until getNativeInstance() is called

        mShader = shader;