[WIP] Speculatively launch Service Workers on mouse/touch events.

third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in

 // http://dev.chromium.org/blink/runtime-enabled-features
 //
 // This list is used to generate RuntimeEnabledFeatures.h/cpp which contains
 // a class that stores static enablers for all experimental features.
 //
 // Each feature can be assigned a "status":
 // status=stable -> Enable this in all Blink configurations.  We are committed to these APIs indefinitely.
 // status=experimental -> In-progress features, Web Developers might play with, but are not on by default in stable.
 // status=test -> Enabled in ContentShell for testing, otherwise off.
 // Features without a status are not enabled anywhere by default.
@@ skipping 187 matching lines @@
 // a runtime-enabled feature name is required for correct IDL syntax.
 // This is a global flag; do not change its status.
 StableBlinkFeatures status=stable
 StackedCSSPropertyAnimations status=experimental
 StyleSharing status=stable
 StyleMatchedPropertiesCache status=stable
 // Do not turn this flag into stable, because many interfaces that should not
 // be shipped would be enabled. Instead, remove the flag from the shipping
 // interface.
 ExperimentalStream status=experimental
+SpeculativeLaunchServiceWorker
 StorageEstimate status=experimental
 Suborigins status=experimental
 // Many websites disable mouse support when touch APIs are available.  We'd
 // like to enable this always but can't until more websites fix this bug.
 // Chromium sets this conditionally (eg. based on the presence of a
 // touchscreen) in ApplyWebPreferences.
 Touch status=stable
 TraceWrappables
 TrustedEventsDefaultAction
 UnsafeES3APIs
@@ skipping 14 matching lines @@
 ScrollCustomization
 ScrollRestoration status=stable
 VisualViewportAPI status=experimental
 WakeLock status=experimental
 WebFontsInterventionV2With2G
 WebFontsInterventionV2WithSlow2G
 WebFontsInterventionTrigger
 Worklet status=test
 WeakMemoryCache
 DoNotUnlockSharedBuffer