This reverts commit 5fd259be.

* Adds a new web benchmark bench_mouse_region_mixed_grid_hover

* Add a benchmark the focuses on Paint object performance

* benchmark updating many child layers

* Add path construction benchmark

* Fix analyzer warnings

* Split file into test+generated code. Add comment

* Add license to new file

* remove unused import

* web benchmarks: separate outliers to reduce noise; add visualization

Collect chrome://tracing data in Web benchmarks

* add docs about writing/running web benchmarks

* explain how to run like devicelab

* add WidgetBuildRecorder docs

* [Web] Add Material Card Infinite Scroll benchmark

Adds a benchmark that makes an infinite list of Material cards
and scrolls it. This benchmark exercises more heavyweight rendering
like shadows and clipping and paths.

* Fix analyzer warnings. Respond to comments

Initial web benchmark harness and 3 benchmarks