Add WebKit logging for first paint and other interesting layout milestones

• Component: WebKit Misc.
• Status: RESOLVED FIXED

[Keith Rollin]

Add some logging to indicate what layout milestones have been reached. This should help us determine if there's a client, rendering, layout, or some other issue when page content does not appear in the client window.

<rdar://problem/49128952>

[Keith Rollin]

The logging is being added to WebFrameLoaderClient::dispatchDidReachLayoutMilestone. This seems like a nice central place to capture layout milestones. However, it will only log notifications that are being sent to clients. It does not indicate all milestones that have occurred. That is, it does not report milestones that are filtered out due to client disinterest. There doesn't seem to be a good central place to capture all milestones, regardless of client interest.

[Keith Rollin]

$ rg 'dispatchDidReachLayoutMilestone' low.txt 
2019-03-22 14:19:50.805015-0700 0x64f1e3   Default     0x0                  1649   0    com.apple.WebKit.WebContent.Development: (WebKit) [com.apple.WebKit:Layout] 0x651bf7ae0 - WebFrameLoaderClient::dispatchDidReachLayoutMilestone: dispatching DidFirstLayoutForFrame, page = 0x7fcffe004e08
2019-03-22 14:19:50.805017-0700 0x64f1e3   Default     0x0                  1649   0    com.apple.WebKit.WebContent.Development: (WebKit) [com.apple.WebKit:Layout] 0x651bf7ae0 - WebFrameLoaderClient::dispatchDidReachLayoutMilestone: dispatching didCompletePageTransition, page = 0x7fcffe004e08
2019-03-22 14:19:50.805029-0700 0x64f1e3   Default     0x0                  1649   0    com.apple.WebKit.WebContent.Development: (WebKit) [com.apple.WebKit:Layout] 0x651bf7ae0 - WebFrameLoaderClient::dispatchDidReachLayoutMilestone: dispatching DidReachLayoutMilestone, page = 0x7fcffe004e08, milestones = DidFirstLayout, DidFirstVisuallyNonEmptyLayout
2019-03-22 14:19:50.805031-0700 0x64f1e3   Default     0x0                  1649   0    com.apple.WebKit.WebContent.Development: (WebKit) [com.apple.WebKit:Layout] 0x651bf7ae0 - WebFrameLoaderClient::dispatchDidReachLayoutMilestone: dispatching DidFirstVisuallyNonEmptyLayoutForFrame, page = 0x7fcffe004e08
2019-03-22 14:19:50.860795-0700 0x64f1e3   Default     0x0                  1649   0    com.apple.WebKit.WebContent.Development: (WebKit) [com.apple.WebKit:Layout] 0x651bf7ae0 - WebFrameLoaderClient::dispatchDidReachLayoutMilestone: dispatching DidReachLayoutMilestone, page = 0x7fcffe004e08, milestones = DidFirstMeaningfulPaint

[Keith Rollin]

<rdar://problem/49128952>

[Keith Rollin]

Created attachment 365762 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 365762 [details]
Patch

Clearing flags on attachment: 365762

Committed r243453: <https://trac.webkit.org/changeset/243453>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.