Add Blink setting to block doc.written scripts on 2g-like networks

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?
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 progressBarCompletion type=ProgressBarCompletion, initial=ProgressBarCompletion::LoadEvent
 
 historyEntryRequiresUserGesture initial=false
 
 # Do we want to try to save screen real estate in the media player by hiding
 # the volume slider / mute button?
 preferHiddenVolumeControls initial=false
 
 # Whether to disallow network fetches for parser blocking scripts in the main
+# frame inserted via document.write, for users on 2G or connections that are
+# effectively 2G.
+disallowFetchForDocWrittenScriptsInMainFrameIfEffectively2G initial=false
+
+# Whether to disallow network fetches for parser blocking scripts in the main
 # frame inserted via document.write, for users on slow connections.
 disallowFetchForDocWrittenScriptsInMainFrameOnSlowConnections initial=false
 
 # Whether to disallow network fetches for parser blocking scripts in the main
 # 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"
 
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 # Whether the CSSPreloadScanner is used for externally CSS preloads. NoPreload
 # indicates that the scanner will be used, but no preloads issued.
 cssExternalScannerNoPreload initial=false
 cssExternalScannerPreload initial=false
 
 browserSideNavigationEnabled initial=false
 
 # Some platforms have media subsystems which are too buggy to allow preloading
 # of content by default. See http://crbug.com/612909 for details.
 forcePreloadNoneForMediaElements initial=false