taiyo@chromium.org chrome-prerendering@google.com This metric counts the number of the update of speculation rules preloading, classified by the reason for updates. Currently, this is introduced to measure the overall impact of BFCache retrigger(crbug.com/1449163). This metric is recorded when UpdateSpeculationCandidates is called on DocumentSpeculationRules. isaboori@google.com spelchat@chromium.org jbroman@chromium.org portals-team@google.com The output of many predictors is a logit score. To use this score for binary classification, we compare it to a threshold. If the score is above the threshold, we classify the instance as positive; otherwise, we classify it as negative. Threshold choice affects classifier precision and recall. There is a trade-off between precision and recall. If we set the threshold too low, we will have high precision but low recall. If we set the threshold too high, we will have high recall but low precision. To choose the best threshold, we can use ROC curves, precision-recall curves, or logit-precision and logit-recall curves. `ExperimentalPreloadingPrediction` helps us collect the UMA data required to achieve this. isaboori@google.com spelchat@chromium.org sreejakshetty@chromium.org jbroman@chromium.org chrome-brapp-loading@chromium.org After the user starts a new navigation, the outcome of the {PreloadingPredictor} preloading predictor is recorded as a true positive or a false positive. These statistics are used to compute precision of the preloading predictor. The statistics about negative cases are not required to compute the precision and are not recorded here. isaboori@google.com spelchat@chromium.org sreejakshetty@chromium.org jbroman@chromium.org chrome-brapp-loading@chromium.org After the user starts a new navigation, the outcome of any eligible {PreloadingPredictor} preloading predictor is recorded as a true positive or a false negative. These statistics are used to compute recall of the preloading predictor. The statistics about false positive and true negative cases are not required to compute the recall and are not recorded here. kenoss@chromium.org chrome-prerendering@google.com Records how many times `PrefetchDataPipeTee::Clone()` is called when the method failed. {PrefetchDataPipeTeeStateLoadingOrSizeExceeded} indicates `PrefetchDataPipeTee::State` at the failure. It is used for investigation crbug.com/374039756. kenoss@chromium.org chrome-prerendering@google.com Records the `PrefetchDataPipeTee::State` at `PrefetchDataPipeTee`'s destructor. It is used for investigation crbug.com/374039756. kenoss@chromium.org chrome-prerendering@google.com Records `true` when `PrefetchResponseReader::CreateRequestHandler` couldn't get valid `body`. `false` is never recorded. It is used for investigation crbug.com/374039756. adithyas@chromium.org portals-team@google.com Records the final PrefetchStatus value for a PrefetchContainer. The value is recorded when a prefetch fails (in the failure case), or when the PrefetchContainer is destroyed (in all other cases). taiyo@chromium.org chrome-prerendering@google.com Records the time spent blocking the thread on `PrePrefetchServiceImpl::StartPrePrefetchRequestInternal()` waiting for `PrePrefetchServiceCore::StartPrePrefetchRequest` to complete execution on its core sequence task runner. taiyo@chromium.org chrome-prerendering@google.com Records the outcome of starting a PrePrefetch request (i.e. whether `PrePrefetchContainer` is started or failed and the reason why). Recorded during `PrePrefetchServiceCore::StartPrePrefetchRequest()`. jbroman@chromium.org portals-team@google.com Records the number of active contents in the same BrowsingInstance as a frame which is, or would be, swapped to a new one due to use of a cross-site prefetch, when this determination is being made on navigation. The proportion of these which is greater than 1 is a rough upper bound for the cases where this might be observable due to an opener relationship. mcnee@chromium.org chrome-brapp-loading@chromium.org Records whether prerendering a back navigation is possible at the time of the prediction of a back navigation by {PreloadingPredictor}. isaboori@google.com spelchat@chromium.org sreejakshetty@chromium.org jbroman@chromium.org chrome-brapp-loading@chromium.org After the user starts a new navigation, the outcome of the preloading attempt of type {PreloadingType} that is triggered by {PreloadingPredictor} is recorded as a true positive or a false positive. These statistics are used to compute precision of the preloading attempt. The statistics about negative cases are not required to compute the precision and are not recorded here. isaboori@google.com spelchat@chromium.org sreejakshetty@chromium.org jbroman@chromium.org chrome-brapp-loading@chromium.org After the user starts a new navigation, the outcome of any eligible preloading attempt of type {PreloadingType} that is triggered by {PreloadingPredictor} or the lack of an attempt by an eligible predictor is recorded as a true positive or a false negative. These statistics are used to compute recall of the preloading attempt. The statistics about false positive and true negative cases are not required to compute the recall and are not recorded here. spelchat@chromium.org sreejakshetty@chromium.org jbroman@chromium.org liuwilliam@chromium.org chrome-brapp-loading@chromium.org Records the triggering outcome of a preloading attempt of type {PreloadingType} and triggered by {PreloadingPredictor} that happened on the previous page load at the time a new navigation is started. kenoss@chromium.org chrome-prerendering@google.com FirstContentfulPaint without foreground filtering. Recorded when {InitiatorLocation}, {NavigationDestinationSuffix}, and {UsedInstantLoad}. kenoss@chromium.org chrome-prerendering@google.com FirstContentfulPaint. Recorded when {InitiatorLocation}, {NavigationDestinationSuffix}, and {UsedInstantLoad}. kenoss@chromium.org chrome-prerendering@google.com FirstContentfulPaint. Recorded when {WithPreloadSuffix}. Note: This is going to be obsolete. Use PreloadServingMetrics.PageLoad.Clients.PaintTiming.NavigationToFirstContentfulPaint.All.All.{{UsedInstantLoad}} instead. robertlin@chromium.org chrome-prerendering@google.com Recorded when navigation finishes. Records the instant load technology used for the navigation. Evaluated for {ChromeInitiatorLocation} and for {NavigationDestinationSuffix}. kenoss@chromium.org chrome-prerendering@google.com The duration from when the used prefetch container is added to the start of prefetch matching. Recorded when {PreloadServingMetricsPrefix} and the prefetch matching ended as actual match. kenoss@chromium.org chrome-prerendering@google.com The number of prefetches that are matched with a navigation. Recorded when {PreloadServingMetricsPrefix}. kenoss@chromium.org chrome-prerendering@google.com Whether a prefetch ahead of prerender existed at the timing of prefetch matching. Recorded when {PreloadServingMetricsPrefix}. kenoss@chromium.org chrome-prerendering@google.com The combination of `PrefetchPotentialCandidateCollectResult`, `PrefetchServableState`, and `PrefetchMatchResolverAction`. See `GetCodeOfPotentialCandidateCollectResultAndServableStateAndMatcherAction()` for the details of the value. Recorded when {PreloadServingMetricsPrefix} and a prefetch ahead of prerender exisited. kenoss@chromium.org chrome-prerendering@google.com The combination of `PrefetchPotentialCandidateServingResult`, `PrefetchServableState`, and `PrefetchMatchResolverAction`. Recorded when {PreloadServingMetricsPrefix} and a prefetch ahead of prerender exisited. kenoss@chromium.org chrome-prerendering@google.com The status of the prefetch at the timing of prefetch matching. Recorded when {PreloadServingMetricsPrefix} and a prefetch ahead of prerender exisited. kenoss@chromium.org chrome-prerendering@google.com The index of the prefetch in the queue, plus one. 0 if the prefetch is not in the queue at the timing of prefetch matching. Recorded when {PreloadServingMetricsPrefix} and a prefetch ahead of prerender exisited. kenoss@chromium.org chrome-prerendering@google.com The size of the prefetch queue at the timing of prefetch matching. Recorded when {PreloadServingMetricsPrefix} and a prefetch ahead of prerender exisited. kenoss@chromium.org chrome-prerendering@google.com The servable state of the prefetch and the PrefetchMatchResolver's action taken. Recorded when {PreloadServingMetricsPrefix} and a prefetch ahead of prerender exisited. kenoss@chromium.org chrome-prerendering@google.com Whether the first prefetch matching for a navigation started as potential match. Recorded when {PreloadServingMetricsPrefix}. kenoss@chromium.org chrome-prerendering@google.com Whether the first prefetch matching for a navigation started as potential match with prefetch ahead of prerender. Recorded when {PreloadServingMetricsPrefix} and the navigation is prerender initial navigation. kenoss@chromium.org chrome-prerendering@google.com Whether the first prefetch matching for a navigation ended as actual match. Recorded when {PreloadServingMetricsPrefix}. kenoss@chromium.org chrome-prerendering@google.com Duration for the first prefetch matching for a navigation. Recorded when {PreloadServingMetricsPrefix}, the first prefetch matching started as potential match, and {PreloadServingMetricsActualMatchSuffix}. kenoss@chromium.org chrome-prerendering@google.com The number of initial candidates of the first prefetch matching for a navigation. Recorded when {PreloadServingMetricsPrefix} and the first prefetch matching started as a potential match. kenoss@chromium.org chrome-prerendering@google.com The number of blocking initial candidates of the first prefetch matching for a navigation. Recorded when {PreloadServingMetricsPrefix} and the first prefetch matching started as a potential match. kenoss@chromium.org chrome-prerendering@google.com `PrefetchPotentialCandidateServingResult` of the last candidate in the first prefetch matching. Recorded when {PreloadServingMetricsPrefix} and the first prefetch matching started as a potential match. kenoss@chromium.org chrome-prerendering@google.com `PrefetchPotentialCandidateServingResult` of prefetch ahead of prerender in the first prefetch matching. Recorded when {PreloadServingMetricsPrefix}, the navigation is prerender initial navigation, and the prefetch ahead of prerender is potential match.