Auto merge of #12741 - changm:shader, r=ConnorGBrewster

update servo to use webrender shaders

<!-- Please describe your changes on the following line: -->
Pulls shaders from webrender and update the webrender commit.
---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X ] `./mach build -d` does not report any errors
- [ X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [X ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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components/servo/Cargo.lock

@@ -2554,7 +2554,7 @@ dependencies = [
 [[package]]
 name = "webrender"
 version = "0.1.0"
-source = "git+https://github.com/servo/webrender#eebe599cab295271900d7fbbe3017232dcbba867"
+source = "git+https://github.com/servo/webrender#66b7134918a56c561cbdf72ab284f5da83459ec4"
 dependencies = [
  "app_units 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "bit-set 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",

ports/cef/Cargo.lock

@@ -2416,7 +2416,7 @@ dependencies = [
 [[package]]
 name = "webrender"
 version = "0.1.0"
-source = "git+https://github.com/servo/webrender#eebe599cab295271900d7fbbe3017232dcbba867"
+source = "git+https://github.com/servo/webrender#66b7134918a56c561cbdf72ab284f5da83459ec4"
 dependencies = [
  "app_units 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "bit-set 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",

resources/shaders/ps_border.fs.glsl

@@ -28,7 +28,7 @@ vec4 draw_dotted_edge() {
   // like firefox.
   float circleSpacing = diameter * 2.2;
 
-  vec2 size = vec2(vBorders.z, vBorders.w);
+  vec2 size = vBorders.zw;
   // Get our position within this specific segment
   vec2 position = vDevicePos - vBorders.xy;
 
@@ -68,15 +68,16 @@ vec2 get_dashed_nudge_factor(vec2 dash_size, bool is_corner) {
   bool xAxisFudge = vBorders.z > vBorders.w;
   if (xAxisFudge) {
     return vec2(dash_size.x / 2.0, 0);
-  } else {
-    return vec2(0.0, dash_size.y / 2.0);
   }
+
+  return vec2(0.0, dash_size.y / 2.0);
 }
 
 vec4 draw_dashed_edge(bool is_corner) {
   // Everything here should be in device pixels.
   // We want the dot to be roughly the size of the whole border spacing
   // 5.5 here isn't a magic number, it's just what mostly looks like FF/Chrome
+  // TODO: Investigate exactly what FF does.
   float dash_interval = min(vBorders.w, vBorders.z) * 5.5;
   vec2 edge_size = vec2(vBorders.z, vBorders.w);
   vec2 dash_size = vec2(dash_interval / 2.0, dash_interval / 2.0);
@@ -143,6 +144,8 @@ void draw_dashed_border(void) {
   }
 }
 
+// TODO: Investigate performance of this shader and see
+//       if it's worthwhile splitting it / removing branches etc.
 void main(void) {
 	if (vRadii.x > 0.0 &&
 		(distance(vRefPoint, vLocalPos) > vRadii.x ||
@@ -178,7 +181,6 @@ void main(void) {
     default:
     {
       discard;
-      break;
     }
   }
 }

resources/shaders/ps_border.vs.glsl

@@ -107,7 +107,5 @@ void main(void) {
     vDevicePos = vi.global_clamped_pos;
 
     // These are in device space
-    vBorders = vec4(border.info.local_rect.x, border.info.local_rect.y,
-                    border.info.local_rect.z,
-                    border.info.local_rect.w) * uDevicePixelRatio;
+    vBorders = border.info.local_rect * uDevicePixelRatio;
 }