`complex_layout_scroll_perf__devtools_memory`: memory regression on dart roll

We are seeing a memory in the `complex_layout_scroll_perf__devtools_memory` after a dart roll.

@rmacnak-google can you please take a look since this is possibly related to the memory changes that were also affecting things like the back button memory usage.

## skiaperf

https://flutter-flutter-perf.luci.app/e/?begin=1782420443&enable_chart_tooltip=true&end=1782756120&keys=Xbe8acc22508613dc839a6667ffa99565&plotSummary=true&selected=commit%3D2808494%26name%3D%252Carch%253Dintel%252Cbranch%253Dmaster%252Cconfig%253Ddefault%252Cdevice_type%253Dmokey%252Cdevice_version%253Dnone%252Chost_type%253Dlinux%252Csub_result%253DmaxAdbTotal%252Ctest%253Dcomplex_layout_scroll_perf__devtools_memory%252C%26tableCol%3D2%26tableRow%3D1526&use_titles=true&xbaroffset=2808494

Start with the linked skiaperf chart for complex_layout_scroll_perf__devtools_memory and compare memory results around the Dart roll. Trace the regression to the relevant memory changes, then verify that the benchmark no longer shows the regression.

Written by the indexing model from the issue text.