Update benchmarks for JS performance improvements

As expected, this substantially improves the JS performance in
logic-heavy benchmarks. I believe the other changes are just noise.

perf.md

@@ -4,7 +4,7 @@ the benefit Dart Sass could provide relative to other implementations.
 This was tested against:
 
 * libsass 0f3d6ad1 and sassc 4674821 compiled with g++ (Debian 7.3.0-18) 7.3.0.
-* Dart Sass 088fc28 on Dart 2.4.0 and Node v12.0.0.
+* Dart Sass 50a45a7 on Dart 2.4.0 and Node v12.0.0.
 * Ruby Sass 8d1edc76 on ruby 2.5.3p105 (2018-10-18 revision 65156) [x86_64-linux].
 
 on Debian x64 with Intel Xeon E5-1650 v3 @ 3.50GHz. The Dart Sass
@@ -20,148 +20,149 @@ I ran five instances of each configuration and recorded the fastest time.
 
 Running on a file containing 4 instances of `.foo {a: b}`:
 
-* sassc: 0.004s
-* Dart Sass from a script snapshot: 0.219s
-* Dart Sass native executable: 0.020s
-* Dart Sass on Node.js: 0.200s
-* Ruby Sass with a hot cache: 0.155s
+* sassc: 0.005s
+* Dart Sass from a script snapshot: 0.216s
+* Dart Sass native executable: 0.018s
+* Dart Sass on Node.js: 0.209s
+* Ruby Sass with a hot cache: 0.148s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
-* 5.0x slower than libsass
-* 10.0x faster than Dart Sass on Node
-* 7.8x faster than Ruby Sass
+* 3.6x slower than libsass
+* 11.6x faster than Dart Sass on Node
+* 8.2x faster than Ruby Sass
 
 ## Large Plain CSS
 
 Running on a file containing 2^17 instances of `.foo {a: b}`:
 
-* sassc: 1.714s
-* Dart Sass from a script snapshot: 1.606s
-* Dart Sass native executable: 1.547s
-* Dart Sass on Node.js: 2.672s
-* Ruby Sass with a hot cache: 11.145s
+* sassc: 1.705s
+* Dart Sass from a script snapshot: 1.550s
+* Dart Sass native executable: 1.518s
+* Dart Sass on Node.js: 2.765s
+* Ruby Sass with a hot cache: 10.965s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
 * 1.1x faster than libsass
-* 1.7x faster than Dart Sass on Node
+* 1.8x faster than Dart Sass on Node
 * 7.2x faster than Ruby Sass
 
 ## Preceding Sparse `@extend`
 
 Running on a file containing `.x {@extend .y}`, 2^17 instances of `.foo {a: b}`, and then `.y {a: b}`:
 
-* sassc: 1.750s
-* Dart Sass from a script snapshot: 1.602s
-* Dart Sass native executable: 1.585s
-* Dart Sass on Node.js: 2.782s
-* Ruby Sass with a hot cache: 17.012s
+* sassc: 1.712s
+* Dart Sass from a script snapshot: 1.613s
+* Dart Sass native executable: 1.582s
+* Dart Sass on Node.js: 2.739s
+* Ruby Sass with a hot cache: 16.472s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
 * 1.1x faster than libsass
-* 1.8x faster than Dart Sass on Node
-* 10.7x faster than Ruby Sass
+* 1.7x faster than Dart Sass on Node
+* 10.4x faster than Ruby Sass
 
 ## Following Sparse `@extend`
 
 Running on a file containing `.y {a: b}`, 2^17 instances of `.foo {a: b}`, and then `.x {@extend .y}`:
 
-* sassc: 1.724s
-* Dart Sass from a script snapshot: 1.610s
-* Dart Sass native executable: 1.568s
-* Dart Sass on Node.js: 2.712s
-* Ruby Sass with a hot cache: 16.670s
+* sassc: 1.701s
+* Dart Sass from a script snapshot: 1.568s
+* Dart Sass native executable: 1.543s
+* Dart Sass on Node.js: 2.821s
+* Ruby Sass with a hot cache: 16.469s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
 * 1.1x faster than libsass
-* 1.7x faster than Dart Sass on Node
-* 10.6x faster than Ruby Sass
+* 1.8x faster than Dart Sass on Node
+* 10.7x faster than Ruby Sass
 
 ## Preceding Dense `@extend`
 
 Running on a file containing `.bar {@extend .foo}` followed by 2^17 instances of `.foo {a: b}`:
 
-* sassc: 2.290s
-* Dart Sass from a script snapshot: 2.476s
-* Dart Sass native executable: 2.566s
-* Dart Sass on Node.js: 5.399s
-* Ruby Sass with a hot cache: 29.002s
+* sassc: 2.260s
+* Dart Sass from a script snapshot: 2.405s
+* Dart Sass native executable: 2.526s
+* Dart Sass on Node.js: 5.612s
+* Ruby Sass with a hot cache: 28.690s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
 * 1.1x slower than libsass
-* 2.1x faster than Dart Sass on Node
-* 11.3x faster than Ruby Sass
+* 2.2x faster than Dart Sass on Node
+* 11.4x faster than Ruby Sass
 
 ## Following Dense `@extend`
 
 Running on a file containing 2^17 instances of `.foo {a: b}` followed by `.bar {@extend .foo}`:
 
-* sassc: 2.317s
-* Dart Sass from a script snapshot: 2.381s
-* Dart Sass native executable: 2.461s
-* Dart Sass on Node.js: 5.481s
-* Ruby Sass with a hot cache: 29.197s
+* sassc: 2.289s
+* Dart Sass from a script snapshot: 2.396s
+* Dart Sass native executable: 2.457s
+* Dart Sass on Node.js: 6.319s
+* Ruby Sass with a hot cache: 28.708s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
 * 1.1x slower than libsass
-* 2.2x faster than Dart Sass on Node
-* 11.9x faster than Ruby Sass
+* 2.6x faster than Dart Sass on Node
+* 11.7x faster than Ruby Sass
 
 ## Bootstrap
 
 Running on a file containing 16 instances of importing the Bootstrap framework:
 
-* sassc: 0.763s
-* Dart Sass from a script snapshot: 1.613s
-* Dart Sass native executable: 0.992s
-* Dart Sass on Node.js: 3.529s
-* Ruby Sass with a hot cache: 12.969s
+* sassc: 0.767s
+* Dart Sass from a script snapshot: 1.534s
+* Dart Sass native executable: 0.955s
+* Dart Sass on Node.js: 3.156s
+* Ruby Sass with a hot cache: 12.521s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
-* 1.3x slower than libsass
-* 3.6x faster than Dart Sass on Node
+* 1.2x slower than libsass
+* 3.3x faster than Dart Sass on Node
 * 13.1x faster than Ruby Sass
 
 ## a11ycolor
 
 Running on a file containing test cases for a computation-intensive color-processing library:
 
-* sassc: 0.262s
-* Dart Sass from a script snapshot: 0.805s
-* Dart Sass native executable: 0.612s
-* Dart Sass on Node.js: 1.876s
-* Ruby Sass with a hot cache: 5.396s
+* sassc: 0.248s
+* Dart Sass from a script snapshot: 0.736s
+* Dart Sass native executable: 0.565s
+* Dart Sass on Node.js: 1.043s
+* Ruby Sass with a hot cache: 5.091s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
 * 2.3x slower than libsass
-* 3.1x faster than Dart Sass on Node
-* 8.8x faster than Ruby Sass
+* 1.8x faster than Dart Sass on Node
+* 9.0x faster than Ruby Sass
 
 ## Susy
 
 Running on a file containing test cases for the computation-intensive Susy grid framework:
 
-* sassc: 0.244s
+* sassc: 0.248s
 * Dart Sass from a script snapshot: 0.673s
-* Dart Sass native executable: 0.248s
-* Dart Sass on Node.js: 1.361s
-* Ruby Sass with a hot cache: 1.576s
+* Dart Sass native executable: 0.237s
+* Dart Sass on Node.js: 0.990s
+* Ruby Sass with a hot cache: 1.527s
 
 Based on these numbers, Dart Sass from a native executable is approximately:
 
 * identical to libsass
-* 5.5x faster than Dart Sass on Node
+* 4.2x faster than Dart Sass on Node
 * 6.4x faster than Ruby Sass
 
 # Prior Measurements
 
+* [1.22.4](https://github.com/sass/dart-sass/blob/a7172a2b1dd48b339e5d57159ed364ffb9f5812e/perf.md).
 * [1.20.2](https://github.com/sass/dart-sass/blob/4b7699291c9f69533d25980d23b0647266b665f2/perf.md).
 * [1.13.4](https://github.com/sass/dart-sass/blob/b6ccc91a138e75420227ff79381c5f70e60254f1/perf.md).
 * [1.6.0](https://github.com/sass/dart-sass/blob/048cbe197a77e1cf4b837a40a5acb737e949fd5c/perf.md).