[gtk+] gsk: Add missing Mozilla copyright header

[Benjamin Otte <otte src gnome org>]

commit 3c8518dce38f92d86cbfe523df94fdf666e07017
Author: Benjamin Otte <otte redhat com>
Date:   Mon Dec 26 17:06:10 2016 +0100

    gsk: Add missing Mozilla copyright header
    
    I stole one of their shader functions, and if I steal, I might as well
    do it right.

 gsk/resources/vulkan/color-clip-rounded.frag.glsl |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/gsk/resources/vulkan/color-clip-rounded.frag.glsl 
b/gsk/resources/vulkan/color-clip-rounded.frag.glsl
index 9825f78..515a998 100644
--- a/gsk/resources/vulkan/color-clip-rounded.frag.glsl
+++ b/gsk/resources/vulkan/color-clip-rounded.frag.glsl
@@ -12,6 +12,11 @@ struct RoundedRect {
   vec4 corners;
 };
 
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
 float clip(vec2 pos, RoundedRect r) {
   vec2 ref_tl = r.bounds.xy + vec2( r.corners.x,  r.corners.x);
   vec2 ref_tr = r.bounds.zy + vec2(-r.corners.y,  r.corners.y);