Incompatibility with flutter candidate 4f49888 and benchmarks

[srawlins]

When attempting to bump the flutter candidate to 4f49888a06baf5c52562075c0e2e3163bb4cdfda (from 86327198ff0678f46cbdfb3e12f1759d03aa768d), we see failures in the benchmarks CI task:

https://github.com/flutter/devtools/actions/runs/18231277406/job/51915214753?pr=9454

              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              ...
            ]
     Which: has length of <44>
  
  package:matcher                               expect
  benchmark/devtools_benchmarks_test.dart 81:5  _runBenchmarks
  Expected: an object with length of <30>
    Actual: [
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              Instance of 'BenchmarkScore',
              ...
            ]
     Which: has length of <44>
  
  package:matcher                               expect
  benchmark/devtools_benchmarks_test.dart 81:5  _runBenchmarks

@elliette notes:

I'm guessing it's not actually the wasm build (like it should be) but the JS build, because extra frames are included in the JS benchmarks, see https://github.com/flutter/packages/blob/e401aeb3aae46b82ce26096d960900748a13131a/packages/web_benchmarks/lib/src/metrics.dart#L152-L155

[elliette]

I bisected the Flutter commits, this is the change that caused the regression: flutter/flutter#175392

Based on the PR description, it seems like it is expected that the skwasm renderer now emits the same frame events as the canvaskit renderer. If that is indeed the case (@harryterkelsen @mdebbar to confirm) I think web_benchmarks should be updated here and published: https://github.com/flutter/packages/blob/1c0be204c45eea42927eb6005bb45f16a8fffb07/packages/web_benchmarks/lib/src/metrics.dart#L152-L155