[DevTools] Switch from blink-based to content-based touch emulation.

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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 imagesEnabled initial=true, invalidate=ImageLoading
 
 javaEnabled initial=false
 pluginsEnabled initial=false
 
 viewportEnabled initial=false, invalidate=ViewportDescription
 viewportMetaEnabled initial=false
 
 dnsPrefetchingEnabled initial=false, invalidate=DNSPrefetching
 
-touchEventEmulationEnabled initial=false
 
 # FIXME: This is a temporary flag and should be removed once
 # accelerated overflow scroll is ready (crbug.com/254111).
 compositorDrivenAcceleratedScrollingEnabled initial=false, invalidate=AcceleratedCompositing
 
 # FIXME: This is a temporary flag and should be removed
 # when squashing is ready. (crbug.com/261605)
 layerSquashingEnabled initial=false
 
 # Clients that execute script should call ScriptController::canExecuteScripts()
 # instead of this function. ScriptController::canExecuteScripts() checks the
 # HTML sandbox, plug-in sandboxing, and other important details.
 scriptEnabled initial=false, invalidate=ScriptEnable
 
 # Compensates for poor text legibility on mobile devices. This value is
 # multiplied by the font scale factor when performing text autosizing of
 # websites that do not set an explicit viewport description.
 deviceScaleAdjustment type=double, initial=1.0, invalidate=TextAutosizing