slideshow: Make sure the slide is fully opaque in Honeycomb

On Windows, the text is rendered with 0 of alpha, which is an issue in
this transition as it enables GL_BLEND.

Change-Id: I45fe32ccf77854e758eddc33f300791d4cdd6904
diff --git a/slideshow/opengl/honeycombFragmentShader.glsl b/slideshow/opengl/honeycombFragmentShader.glsl
index 325e393..7e52951 100644
--- a/slideshow/opengl/honeycombFragmentShader.glsl
+++ b/slideshow/opengl/honeycombFragmentShader.glsl
@@ -26,7 +26,7 @@ bool isBorder(vec2 point)

void main()
{
    vec4 fragment = texture2D(slideTexture, texturePosition);
    vec4 fragment = vec4(texture2D(slideTexture, texturePosition).rgb, 1.0);
    vec3 lightVector = vec3(0.0, 0.0, 1.0);
    float light = max(dot(lightVector, normal), 0.0);
    if (hexagonSize > 1.0) {