Bug 77278 – Web Inspector: revalidated cached scripts have misleading receive/parse times in Timeline

• Component: Web Inspector (Deprecated)
• Status: RESOLVED INVALID

[Brian Burg]

Created attachment 124439 [details]
ga.js is reported as parsed, executed before it is received

Revalidated (304) cached scripts will be parsed and executed before they show as being received in the Timeline panel. This does not affect normal resource loads.

After some investigation, the problem seems to be that cached resource clients are being notified of revalidation before ResourceLoader clients are being notified of the response being received. The latter can trigger parsing and execution if the cache client happens to be the document parser. I'm unsure how to fix this, since there seem to be a lot of subtle invariants in the resource loading code.

I've attached a screenshot demonstrating the incorrect timeline pill ordering, as well as a useful stack trace which seems to show the start of problems.

[Brian Burg]

Created attachment 124440 [details]
Useful stack trace screenshot

Note that memoryCache()->revalidationSucceeded(...) eventually leads to HTMLDocumentParser::notifyFinished(), causing parsing to occur on for the pending script that blocks parsing. But, InspectorInstrumentation::willReceiveResourceResponse() is eventually called by ResourceLoader::didReceiveResponse.

[Brian Burg]

Closing as invalid, as this bug pertains to the old inspector UI and/or its tests.
Please file a new bug (https://www.webkit.org/new-inspector-bug) if the bug/feature/issue is still relevant to WebKit trunk.