[tracing] Emit trace LCP/FCP events more consistently [chromium/src : main]
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Etienne Pierre-Doray (Gerrit)
Apr 21, 2026, 4:12:07 PM (8 days ago) Apr 21
to Minoru Chikamune, Michal Mocny, Chromium LUCI CQ, chromium...@chromium.org, bmcquad...@chromium.org, core-web-vita...@chromium.org, csharris...@chromium.org, loading-rev...@chromium.org, speed-metrics...@chromium.org, speed-metr...@chromium.org
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Etienne Pierre-Doray added 1 comment![]( "Open in Gerrit")
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Minoru Chikamune (Gerrit)
Apr 21, 2026, 9:40:23 PM (8 days ago) Apr 21
to Etienne Pierre-Doray, Minoru Chikamune, Michal Mocny, Chromium LUCI CQ, chromium...@chromium.org, bmcquad...@chromium.org, core-web-vita...@chromium.org, csharris...@chromium.org, loading-rev...@chromium.org, speed-metrics...@chromium.org, speed-metr...@chromium.org
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Minoru Chikamune added 1 comment![]( "Open in Gerrit")
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File-level comment, Patchset 13 (Latest):
Minoru Chikamune . unresolved
Thank you for working on this. But when I tried this CL locally, it immediately crashed.
```
out/Linux/chrome https://www.google.com/search?q=cat
...
Received signal 6
#0 0x7f9d25cb46f2 base::debug::CollectStackTrace() [../../base/debug/stack_trace_posix.cc:1050:7]
#1 0x7f9d25c9821e base::debug::StackTrace::StackTrace() [../../base/debug/stack_trace.cc:280:20]
#2 0x7f9d25cb4158 base::debug::(anonymous namespace)::StackDumpSignalHandler() [../../base/debug/stack_trace_posix.cc:483:3]
#3 0x7f9d10240a70 (/usr/lib/x86_64-linux-gnu/libc.so.6+0x40a6f)
#4 0x7f9d102973dc (/usr/lib/x86_64-linux-gnu/libc.so.6+0x973db)
#5 0x7f9d10240942 gsignal
#6 0x7f9d102284ac abort
#7 0x7f9d195c95c2 std::__Cr::__libcpp_verbose_abort()
#8 0x555da96a9a2d UmaPageLoadMetricsObserver::EmitPageLoadTimelineTraceEventEnd()
#9 0x555da96a94c7 UmaPageLoadMetricsObserver::OnStart()
[../../components/page_load_metrics/browser/observers/core/uma_page_load_metrics_observer.cc:374:3]
#10 0x555da90255d7 base::RepeatingCallback<>::Run() [../../base/functional/callback.h:346:12]
```
I had to update the following lines, but the `ParseStartToFCP` became a strange state.
```
modified components/page_load_metrics/browser/observers/core/uma_page_load_metrics_observer.cc
@@ -1432,9 +1432,10 @@ void UmaPageLoadMetricsObserver::EmitPageLoadTimelineTraceEventEnd(
}
auto trace_begin_event = std::exchange(trace_begin_event_, std::nullopt);
- DCHECK(trace_begin_event);
- DCHECK_EQ(trace_begin_event->name, name);
- DCHECK_EQ(trace_begin_event->navigation_id, GetDelegate().GetNavigationId());
+ if (!trace_begin_event || trace_begin_event->name != name ||
+ trace_begin_event->navigation_id != GetDelegate().GetNavigationId()) {
+ return;
+ }
auto track = *timeline_track_;
const base::TimeTicks effective_end =
```
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Etienne Pierre-Doray (Gerrit)
Apr 22, 2026, 1:50:40 PM (7 days ago) Apr 22
to Minoru Chikamune, Michal Mocny, Chromium LUCI CQ, chromium...@chromium.org, bmcquad...@chromium.org, core-web-vita...@chromium.org, csharris...@chromium.org, loading-rev...@chromium.org, speed-metrics...@chromium.org, speed-metr...@chromium.org
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Etienne Pierre-Doray
Whoops, it didn't handle a tracing session starting during navigation. This should be fixed now.
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Minoru Chikamune (Gerrit)
Apr 27, 2026, 9:27:22 PM (2 days ago) Apr 27
to Etienne Pierre-Doray, Minoru Chikamune, Michal Mocny, Chromium LUCI CQ, chromium...@chromium.org, bmcquad...@chromium.org, core-web-vita...@chromium.org, csharris...@chromium.org, loading-rev...@chromium.org, speed-metrics...@chromium.org, speed-metr...@chromium.org
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Minoru Chikamune added 1 comment![]( "Open in Gerrit")
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File-level comment, Patchset 15 (Latest):
Minoru Chikamune . resolved
Sorry for my late review. I'll check this CL today. I've been OOO. Sorry.
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Minoru Chikamune (Gerrit)
Apr 28, 2026, 4:55:11 AM (yesterday) Apr 28
to Etienne Pierre-Doray, Minoru Chikamune, Michal Mocny, Chromium LUCI CQ, chromium...@chromium.org, bmcquad...@chromium.org, core-web-vita...@chromium.org, csharris...@chromium.org, loading-rev...@chromium.org, speed-metrics...@chromium.org, speed-metr...@chromium.org
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Minoru Chikamune added 1 comment![]( "Open in Gerrit")
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Minoru Chikamune . unresolved
Sorry for my late review. I'll check this CL today. I've been OOO. Sorry.
Minoru Chikamune
I tried the newest patch, but it seems that the newest patch still has the same problem.
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Minoru Chikamune (Gerrit)
Apr 28, 2026, 4:58:25 AM (yesterday) Apr 28
to Etienne Pierre-Doray, Minoru Chikamune, Michal Mocny, Chromium LUCI CQ, chromium...@chromium.org, bmcquad...@chromium.org, core-web-vita...@chromium.org, csharris...@chromium.org, loading-rev...@chromium.org, speed-metrics...@chromium.org, speed-metr...@chromium.org
Attention needed from Etienne Pierre-Doray
Minoru Chikamune added 1 comment![]( "Open in Gerrit")
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Minoru Chikamune . unresolved
Minoru ChikamuneSorry for my late review. I'll check this CL today. I've been OOO. Sorry.
I tried the newest patch, but it seems that the newest patch still has the same problem.
Minoru Chikamune
Etienne Pierre-Doray (Gerrit)
Apr 28, 2026, 3:46:33 PM (yesterday) Apr 28
to Minoru Chikamune, Michal Mocny, Chromium LUCI CQ, chromium...@chromium.org, bmcquad...@chromium.org, core-web-vita...@chromium.org, csharris...@chromium.org, loading-rev...@chromium.org, speed-metrics...@chromium.org, speed-metr...@chromium.org
Attention needed from Minoru Chikamune
Etienne Pierre-Doray added 1 comment![]( "Open in Gerrit")
Patchset-level comments
Minoru ChikamuneSorry for my late review. I'll check this CL today. I've been OOO. Sorry.
Minoru ChikamuneI tried the newest patch, but it seems that the newest patch still has the same problem.
Before this CL:
Etienne Pierre-Doray
Fixed, thanks for flagging! I was missing closing ParseStartToFCP when the page is hidden.
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