Copy shaders from WR repo.

resources/shaders/ps_angle_gradient.fs.glsl

@@ -0,0 +1,39 @@
+/* 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 offset(int index) {
+    return vOffsets[index / 4][index % 4];
+}
+
+float linearStep(float lo, float hi, float x) {
+    float d = hi - lo;
+    float v = x - lo;
+    if (d != 0.0) {
+        v /= d;
+    }
+    return clamp(v, 0.0, 1.0);
+}
+
+void main(void) {
+    float angle = atan(-vEndPoint.y + vStartPoint.y,
+                        vEndPoint.x - vStartPoint.x);
+    float sa = sin(angle);
+    float ca = cos(angle);
+
+	float sx = vStartPoint.x * ca - vStartPoint.y * sa;
+    float ex = vEndPoint.x * ca - vEndPoint.y * sa;
+    float d = ex - sx;
+
+    float x = vPos.x * ca - vPos.y * sa;
+
+    oFragColor = mix(vColors[0],
+                     vColors[1],
+                     linearStep(sx + d * offset(0), sx + d * offset(1), x));
+
+    for (int i=1 ; i < vStopCount-1 ; ++i) {
+        oFragColor = mix(oFragColor,
+                         vColors[i+1],
+                         linearStep(sx + d * offset(i), sx + d * offset(i+1), x));
+    }
+}