Snippet from log:

	Child-SP          RetAddr           Call Site
	000000d7`f48e9420 00007ffa`8f2ebacd chrome_child!??$_Try_emplace@V?$BasicStringPiece@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@base@@$$V@?$map@V?$BasicStringPiece@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@base@@_NU?$less@V?$BasicStringPiece@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@base@@@std@@V?$allocator@U?$pair@$$CBV?$BasicStringPiece@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@base@@_N@std@@@4@@std@@QEAA?AU?$pair@V?$_Tree_iterator@V?$_Tree_val@U?$_Tree_simple_types@U?$pair@$$CBV?$BasicStringPiece@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@base@@_N@std@@@std@@@std@@@std@@_N@1@$$QEAV?$BasicStringPiece@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@base@@@Z+0x118
	000000d7`f48e9450 00007ffa`8f30f0d0 chrome_child!_invalid_parameter_noinfo+0x19
	000000d7`f48e9490 00007ffa`8f31533d chrome_child!_isatty+0x58
	000000d7`f48e94c0 00007ffa`8f2ec525 chrome_child!__acrt_stdio_begin_temporary_buffering_nolock+0x19
	(Inline Function) --------`-------- chrome_child!__acrt_stdio_temporary_buffering_guard::{ctor}+0x8
	000000d7`f48e94f0 00007ffa`8f2ebc46 chrome_child!<lambda_0a64b6a4deda75c01876f29c44fc5eb3>::operator()+0x35
	000000d7`f48e99f0 00007ffa`8f2ef1a5 chrome_child!__crt_seh_guarded_call<int>::operator()<<lambda_aa279a7bcb127014629d5b1d62c7325d>,<lambda_0a64b6a4deda75c01876f29c44fc5eb3> & __ptr64,<lambda_3323e69fbefe9d1a11713e670d47cdfa> >+0x26
	(Inline Function) --------`-------- chrome_child!__acrt_lock_stream_and_call+0x41
	(Inline Function) --------`-------- chrome_child!common_vfprintf+0x64
	000000d7`f48e9a20 00007ffa`8eaa12ae chrome_child!__stdio_common_vfprintf+0x85
	000000d7`f48e9a90 00007ffa`8eaa1331 chrome_child!WTF::TextPosition::fromOffsetAndLineEndings+0x176
	000000d7`f48e9ad0 00007ffa`8eaa1374 chrome_child!WTF::TextPosition::fromOffsetAndLineEndings+0x1f9
	000000d7`f48e9b00 00007ffa`8da36ff2 chrome_child!WTFLogAlways+0x20
	000000d7`f48e9b30 00007ffa`8da371f2 chrome_child!blink::TraceTrait<blink::FormSubmission>::trace+0x2a2
	000000d7`f48e9b90 00007ffa`8da381c4 chrome_child!blink::TraceTrait<blink::FormSubmission>::trace+0x4a2
	000000d7`f48e9bd0 00007ffa`8d92e3ef chrome_child!blink::FrameFetchContext::resourceRequestCachePolicy+0x284
	000000d7`f48e9c00 00007ffa`8d92de09 chrome_child!blink::ResourceFetcher::initializeResourceRequest+0x3f
	000000d7`f48e9c50 00007ffa`8d9363c1 chrome_child!blink::ResourceFetcher::requestResource+0x359
	000000d7`f48ea030 00007ffa`8d576bef chrome_child!blink::ScriptResource::fetch+0x91
	000000d7`f48ea110 00007ffa`8d57632f chrome_child!blink::ScriptLoader::fetchScript+0x3ef
	000000d7`f48ea590 00007ffa`8d6c74e3 chrome_child!blink::ScriptLoader::prepareScript+0x2ff
	000000d7`f48ea750 00007ffa`8d6c6a9d chrome_child!blink::HTMLScriptRunner::runScript+0xc3
	000000d7`f48ea8f0 00007ffa`8d6b0a87 chrome_child!blink::HTMLScriptRunner::execute+0xfd
	000000d7`f48ea970 00007ffa`8d6b0ac1 chrome_child!blink::HTMLDocumentParser::runScriptsForPausedTreeBuilder+0x57
	000000d7`f48ea9a0 00007ffa`8d6b2988 chrome_child!blink::HTMLDocumentParser::canTakeNextToken+0x31
	000000d7`f48ea9d0 00007ffa`8d6b30b5 chrome_child!blink::HTMLDocumentParser::pumpTokenizer+0x398
	000000d7`f48eab10 00007ffa`8d501dc5 chrome_child!blink::HTMLDocumentParser::insert+0x3a5
	000000d7`f48eaca0 00007ffa`8d501e1d chrome_child!blink::Document::write+0x2f5
	000000d7`f48ead30 00007ffa`8d502213 chrome_child!blink::Document::write+0x2d
	000000d7`f48eadc0 00007ffa`8d2ae044 chrome_child!blink::Document::write+0x1d3
	000000d7`f48eb150 00007ffa`8d2ae11c chrome_child!blink::XPathEvaluator::create+0x11d04
	000000d7`f48eb1f0 00007ffa`8c8c9bc0 chrome_child!blink::XPathEvaluator::create+0x11ddc
	000000d7`f48eb230 00007ffa`8c95b862 chrome_child!v8::internal::FunctionCallbackArguments::Call+0x160
	000000d7`f48eb310 00007ffa`8c951710 chrome_child!v8::internal::CopyChars<unsigned char,unsigned short>+0x622
	000000d7`f48eb430 00007ffa`8c95160b chrome_child!v8::internal::Builtins::Generate_StringPrototypeCharCodeAt+0x29a0
	000000d7`f48eb4d0 000000ca`d26063ab chrome_child!v8::internal::Builtins::Generate_StringPrototypeCharCodeAt+0x289b
	000000d7`f48eb510 00007ffa`8cbe84af 0x000000ca`d26063ab
	000000d7`f48eb518 00000120`36e060e1 chrome_child!v8::internal::Runtime_CallIC_Miss+0xc0f
	000000d7`f48eb520 00000000`beeddead 0x00000120`36e060e1
	000000d7`f48eb528 000000d7`f4ac6130 <Unloaded_Unknown_Module_00000000`00000002>+0xbeeddeab
	000000d7`f48eb530 00000000`beeddead <Unloaded_Unknown_Module_000000d7`f4a30e74>+0x952bc
	000000d7`f48eb538 000000d7`f4ac6130 <Unloaded_Unknown_Module_00000000`00000002>+0xbeeddeab
	000000d7`f48eb540 000000ca`d26062e1 <Unloaded_Unknown_Module_000000d7`f4a30e74>+0x952bc
	000000d7`f48eb548 000000d7`f48eb510 0x000000ca`d26062e1
	000000d7`f48eb550 00000003`00000000 0x000000d7`f48eb510
	000000d7`f48eb558 000000d7`f48eb5c0 0x00000003`00000000
	000000d7`f48eb560 000000ca`d27568fa 0x000000d7`f48eb5c0
	000000d7`f48eb568 00000120`36e04399 0x000000ca`d27568fa

I think that my patch is the most likely (indirect) culprit: https://codereview.chromium.org/2094143005. I suggest we speculatively revert it.

 Issue 624801  has been merged into this issue.

Log: https://build.chromium.org/p/chromium.perf/builders/Win%208%20Perf%20%283%29/builds/4729/steps/system_health.memory_desktop/logs/stdio