[RenderEngine] Allow rounded corners shader to use lower precision.

            float applyCornerRadius(vec2 cropCoords)

            {

                vec2 position = cropCoords - cropCenter;

                // Increase precision here so that a large corner radius doesn't

                // cause floating point error

                highp vec2 dist = abs(position) + vec2(cornerRadius) - cropCenter;

                float plane = length(max(dist, vec2(0.0)));

                // Scale down the dist vector here, as otherwise large corner

                // radii can cause floating point issues when computing the norm

                vec2 dist = (abs(position) - cropCenter + vec2(cornerRadius)) / 16.0;

                // Once we've found the norm, then scale back up.

                float plane = length(max(dist, vec2(0.0))) * 16.0;

                return 1.0 - clamp(plane - cornerRadius, 0.0, 1.0);

            }

            )__SHADER__";