Experiments:
AndroidSigninPromos-Enabled
AppBannerTriggering-Control
AsyncDns-Control
AutofillFieldMetadata-Enabled
AutofillRationalizeFieldTypePredictions-Default
BackgroundTracing-default
BrowserScheduler-AllTasksUserBlocking
CSSExternalScanner-Enabled_ScanOnly
CheckerImaging-Control2
ChromeChannelCanary-Enabled
ChromeHome-Forced_Enabled_Dogfood
ChromeHomeDestroySuggestions-Enabled
ClearOldOnDemandFavicons-Enabled
ContentSuggestionsDebugLog-Enabled_Dogfood
CopylessPaste-Enabled
DataCompressionProxyHoldback-Disabled
DataCompressionProxyPromoVisibility-EnabledWithSnackbarPromo
DataReductionProxySiteBreakdown-Enabled_Dogfood
DynamicExpectCT-DynamicExpectCTEnabled
FixDocumentLeakInAutofillAgent-Default
FreedObjectTracker-Control
HTTP2-Default
KeepAliveRendererForKeepaliveRequests-Enabled_20sec
LoadingWithMojo-Control
MarkNonSecureAs-show-non-secure-passwords-cc-ui
MidiManagerDynamicInstantiation-Enabled_Dogfood
NTPArticleSuggestions-Enabled62-FCS_Dogfood
NTPBreakingNewsPush-Enabled_Dogfood
NTPCondensedLayout-CondensedLayoutWithoutLogo
NTPFaviconsFromNewServer-Enabled512
NTPLessThanEightMostLikelyTilesDevCanary-FourOrMoreMLTiles
NTPMostLikelyFaviconsFromServer-EnabledInclIOS_Dogfood
NTPPopularSites-EnabledGoogleSearchExperiment_Dogfood
NTPUseDdljsonApi-Control62
NetworkQualityEstimator-Control4
NewPhotoPicker-Enabled
OfflinePagesPrefetchingSuggestions-Control_50_Percent
OmniboxBundledExperimentV1-Dev_Android_PhysWebAndNewOmniboxAnswerTypes_Dogfood
OmniboxCombinedSpeculativeServiceWorker-PrewarmingWithServiceWorker
OmniboxPlaceholderExperiment-Unused
PasswordGeneration-Enabled
PersistentHistograms-Enabled50
PreviewsClientLoFi-Enabled_2G_Replace_Server_Placeholders_Dogfood
QUIC-Disabled
ReportingAPI-Enabled
ResourceLoadScheduler-Enabled_bg_limit_16
SafeBrowsingUseLocalBlacklist-Use3PAPI
SearchLiteDataSaver-Experiment_Dogfood
ServiceWorkerScriptStreaming-Enabled
SimpleCachePrefetchExperiment-Prefetch32K
SpeculativeResourcePrefetchingValidation-Default
SubresourceFilter-Control_Dogfood
SyncUSSAutocomplete-Control
TLS13Variant-Experiment3
TabManagementExperiment-Elderberry
ThrottleDelayable-MaxDelayable12_Weight2
UMA-Population-Restrict-dogfood
UMA-Uniformity-Trial-10-Percent-group_07
UMA-Uniformity-Trial-100-Percent-group_01
UMA-Uniformity-Trial-20-Percent-group_04
UMA-Uniformity-Trial-50-Percent-default
UseMojoAudioOutputStreamFactory-Control
V8ContextSnapshot-Enabled
VsyncAlignedInput-Control
WebFontsInterventionV2-Control-1
WheelScrollLatching_AsyncWheelEvents-Control
XGEOVisibleNetworks-Experiment

ktam@, by "Chrome Dev", do you mean 63.0.3223.7 (which is the current recent dev vesrion)?

The suggestions content is there immediately, but the sheet open does look pretty laggy.

Correct. I mean 63.0.3223.7.

One thing we can try here is delaying the toolbar button animation when the sheet is opened since that causes a requestLayout() call. If we stagger the things that are happening on sheet open, we may be able to reduce some of the lag.

A quick update here - Kingston tried disabling a number of experiments to no avail. We are unable to reproduce anywhere besides Kingston's Canary. Kingston was planning to retest on a future Canary push.

Perhaps this is caused to some poor interaction of active experiments. Bernhard, are any of the NTP experiments in #2 new?

+ktam@ to provide more details on experiments he disabled and whether this is still reproducing on current Canary

I disabled all the experiments under NTP and favicon to no effect. The lag is less severe in the current Canary though still noticeable when compared to Dev. (it's <100ms freeze)

These are all of the chrome://flags experiments that I see related to the NTP/favicons/suggestions. By "all the experiments", do you mean all of these or different set?

 - Show popular sites for the New Tab page
 - Breaking News Push
 - Make New Tab Page Snippets more visible
 - Enable Contextual Suggestions
 - Get favicons for content suggestions from a new server
 - Download favicons for NTP tiles from Google
 - Show also lower resolution favicons in NTP tiles
 - Large thumbnails layout for content suggestions cards
 - Use content suggestions thumbnail dominant color
 - Load favicons from Web Manifests (I don't think this affects Zine)
 - Show server-side suggestions on the New Tab page
 - Show assets downloads on the New Tab page
 - Show offline page downloads on the New Tab page
 - Show recently visited bookmarks on the New Tab page
 - Show recent foreign tabs on the New Tab page
 - Notify about new content suggestions available on the New Tab page
 - Condensed NTP layout
 - Condensed NTP tile layout
 - Site Exploration UI
 - Google G in the New Tab page omnibox
 - Enable NTP offline pages
 - Disable minimumfor  server-side tile suggestions on NTP
 - Keep prefetched content suggestions
 - Default content suggestions category order
 - Content suggestions category ranker
 - Use new ddljson API for Doodles

I expect many of these don't affect Chrome Home and/or have been on for a long time, but I'm not familiar enough with any of them to know for sure.

Another thing you could try if your device is connected to a desktop/laptop is to open chrome://inspect/?tracing, which lets you run remote tracing on the device, so we could try to see where the jank is coming from.

mdjones@ did tracing on Kingston's phone, and it provided no useful information. It showed the gap, but no useful information. We tried putting a debug build on Kingston's phone to get more useful information and the debug build din't present the problem.

Hmm.. I can no longer repro this as I migrated to a new phone and apparently canary app data wasn't transferred over. Closing out until we get another repro case.