[gtk+] gl renderer: Use alpha uniform in inset shadow shader

[Timm Bäder <baedert src gnome org>]

commit 3176ae7e517839ca19e1dd9aaee02fbefc852d37
Author: Timm Bäder <mail baedert org>
Date:   Fri Jan 5 18:14:51 2018 +0100

    gl renderer: Use alpha uniform in inset shadow shader

 gsk/resources/glsl/inset_shadow.fs.glsl |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gsk/resources/glsl/inset_shadow.fs.glsl b/gsk/resources/glsl/inset_shadow.fs.glsl
index b6bb87c..87a7205 100644
--- a/gsk/resources/glsl/inset_shadow.fs.glsl
+++ b/gsk/resources/glsl/inset_shadow.fs.glsl
@@ -23,5 +23,5 @@ void main() {
   color = color * clamp (rounded_rect_coverage (outline, f.xy) -
                          rounded_rect_coverage (inside, f.xy - offset),
                          0.0, 1.0);
-  setOutputColor(color);
+  setOutputColor(color * u_alpha);
 }