Extra stuff for webrender-2022.

Here's the overall time to `full` compile everything, webrender vs
webrender-2022:
```
         old    new
- check  15.8s  21.9s
- debug  19.5s  28.4s
- opt    25.0s  38.9s
```
Roughly 1.5x longer.

And here's the time to `full` compile just the final crate:
```
         old    new
- check  1.74s  4.28s
- debug  4.70s  9.92s
- opt    9.58s  19.14s
```
Roughly 2x longer.

Author: nnethercote

collector/benchmarks/README.md

@@ -49,6 +49,10 @@ They mostly consist of real-world crates.
   utilities. Uses huge `match` statements that stress the compiler in unusual
   ways.
 - **webrender**: A web renderer. Used by Firefox and Servo.
+- **webrender-2022**: A web renderer. A large, complex crate used by Firefox
+  and Servo. Webrender isn't released regularly so this is a development
+  version (revision 78502fd). The `-2022` suffix distinguishes it from earlier
+  Webrender versions that used to be used in this benchmark suite.
 - **webrender-wrench**: WebRender's test bench. An executable pulling in large
   dependencies.
 

collector/benchmarks/webrender-2022/0-println.patch

@@ -0,0 +1,12 @@
+diff --git a/webrender/src/scene.rs b/webrender/src/scene.rs
+index 864ed683..08ec78dc 100644
+--- a/webrender/src/scene.rs
++++ b/webrender/src/scene.rs
+@@ -34,6 +34,7 @@ pub struct SceneProperties {
+ 
+ impl SceneProperties {
+     pub fn new() -> Self {
++        println!("testing");
+         SceneProperties {
+             transform_properties: FastHashMap::default(),
+             float_properties: FastHashMap::default(),

collector/benchmarks/webrender-2022/perf-config.json

@@ -1,3 +1,6 @@
 {
-  "category": "primary"
+    "cargo_toml": "webrender/Cargo.toml",
+    "runs": 1,
+    "touch_file": "webrender/src/lib.rs",
+    "category": "primary"
 }