DevTools: add the logging aspect into the PerformanceMonitor

third_party/WebKit/Source/core/frame/Settings.in

 # Defines properties which are available on the Settings object.
 #
 # Please think carefully before adding a new Setting.  Some questions to
 # consider are:
 # - Should this be a RuntimeEnabledFeature instead? Settings are for things
 #   which we support either values of at runtime.  Features are set at renderer
 #   process startup and are never changed. Features also tend to be set to a
 #   value based on the platform or the stability of the code in question, where
 #   as settings both codepaths need to be stable.
 # - How will you ensure test coverage of all relevant values of your setting?
@@ skipping 373 matching lines @@
 # frame inserted via document.write, regardless of connection type.
 disallowFetchForDocWrittenScriptsInMainFrame initial=false
 
 # The autoplay gesture override experiment is described in crbug.com/487345 .
 autoplayExperimentMode type=String, initial="off"
 
 # Whether to invalidate device-dependent media queries and restore scroll positions
 # on frame resize assuming device rotation.
 mainFrameResizesAreOrientationChanges initial=false
 
-# If set to a positive value, emit a console warning once for each non-passive
-# event listener that caused an event to be dispatched to main thread and
-# delayed by more than the specified time (in seconds).
-blockedMainThreadEventsWarningThreshold type=double, initial=0
-
 # Ability to override the default 'passive' value in AddEventListenerOptions. This
 # is useful to demonstrate the power of passive event listeners. This can be removed
 # when there is greater adoption, interventions to force it on and associated devtools
 # to enable it have been shipped.
 passiveListenerDefault type=PassiveListenerDefault, initial=PassiveListenerDefault::False
 
 # Use default interpolation quality to scale bitmap images if quality is not determined
 # in other ways. This can help us writing reftests containing scaled images.
 useDefaultImageInterpolationQuality initial=false
 
@@ skipping 20 matching lines @@
 
 # Spellchecking is enabled by default for elements that do not specify it explicitly
 # using the "spellcheck" attribute.
 spellCheckEnabledByDefault initial=true
 
 # Whether download UI should be hidden for the current page content.
 hideDownloadUI initial=false
 
 # Whether or not to issue range requests for images and show placeholders.
 fetchImagePlaceholders initial=false