[webkit-dev] Experimental features review

[Michael Catanzaro]

Hi,

Last year, we cleaned up experimental features in WebPreferences.yaml 
to ensure no experimental features were enabled by default. Since then 
we have regressed a bit when enabling cool new web features. :) 
Currently we have 12 offenders, listed below. Most likely, the 
category: experimental line should be removed from these features. 
Alternatively, the defaultValue should be changed to either false or 
DEFAULT_EXPERIMENTAL_FEATURES_ENABLED (or something depending on that).

If you know about any of these settings, please keep reading and help 
decide what to do with them:

BlankAnchorTargetImpliesNoOpenerEnabled
ThirdPartyIframeRedirectBlockingEnabled
ScreenCaptureEnabled
WebRTCUnifiedPlanEnabled
WebRTCVP8CodecEnabled
WebRTCH264SimulcastEnabled
WebRTCMDNSICECandidatesEnabled
IntersectionObserverEnabled
VisualViewportAPIEnabled
DarkModeCSSEnabled
WebSQLDisabled
ProcessSwapOnCrossSiteNavigationEnabled

Details:

BlankAnchorTargetImpliesNoOpenerEnabled:
   type: bool
   defaultValue: true
   webcoreBinding: RuntimeEnabledFeatures
   humanReadableName: "Blank anchor target implies rel=noopener"
   humanReadableDescription: "target=_blank on anchor elements implies 
rel=noopener"
   category: experimental

ThirdPartyIframeRedirectBlockingEnabled:
   type: bool
   defaultValue: true
   humanReadableName: "Block top-level redirects by third-party iframes"
   humanReadableDescription: "Block top-level redirects by third-party 
iframes"
   category: experimental

ScreenCaptureEnabled:
  type: bool
  defaultValue: true
  webcoreBinding: RuntimeEnabledFeatures
  condition: ENABLE(MEDIA_STREAM) && PLATFORM(MAC)
  humanReadableName: "ScreenCapture"
  humanReadableDescription: "Enable ScreenCapture"
  category: experimental

WebRTCUnifiedPlanEnabled:
  type: bool
  defaultValue: true
  webcoreBinding: RuntimeEnabledFeatures
  condition: ENABLE(WEB_RTC)
  humanReadableName: "WebRTC Unified Plan"
  humanReadableDescription: "Use WebRTC Unified Plan"
  category: experimental

WebRTCVP8CodecEnabled:
  type: bool
  defaultValue: true
  webcoreBinding: RuntimeEnabledFeatures
  condition: ENABLE(WEB_RTC)
  humanReadableName: "WebRTC VP8 codec"
  humanReadableDescription: "Enable WebRTC VP8 codec"
  category: experimental

WebRTCH264SimulcastEnabled:
  type: bool
  defaultValue: true
  webcoreBinding: RuntimeEnabledFeatures
  condition: ENABLE(WEB_RTC)
  humanReadableName: "WebRTC H264 Simulcast"
  humanReadableDescription: "Enable WebRTC H264 Simulcast"
  category: experimental

WebRTCMDNSICECandidatesEnabled:
  type: bool
  defaultValue: true
  humanReadableName: "WebRTC mDNS ICE candidates"
  humanReadableDescription: "Enable WebRTC mDNS ICE candidates"
  webcoreBinding: RuntimeEnabledFeatures
  category: experimental
  condition: ENABLE(WEB_RTC)

If the above features are to remain experimental, they should be sorted 
lower in the file, below this comment explaining experimental feature 
policy:

# For experimental features:
# The type should be boolean.
# You must provide a humanReadableName and humanReadableDescription for 
all experimental features. They
# are the text exposed to the user from the WebKit client.
# The default value may be either false (for unstable features) or
# DEFAULT_EXPERIMENTAL_FEATURES_ENABLED (for features that are ready for
# wider testing).

More offenders:

IntersectionObserverEnabled:
  type: bool
  defaultValue: true
  humanReadableName: "Intersection Observer"
  humanReadableDescription: "Enable Intersection Observer support"
  webcoreBinding: RuntimeEnabledFeatures
  category: experimental
  condition: ENABLE(INTERSECTION_OBSERVER)

VisualViewportAPIEnabled:
  type: bool
  defaultValue: true
  humanReadableName: "Visual Viewport API"
  humanReadableDescription: "Enable Visual Viewport API"
  category: experimental

DarkModeCSSEnabled:
  type: bool
  defaultValue: true
  humanReadableName: "Dark Mode CSS Support"
  humanReadableDescription: "Enable Dark Mode CSS Support"
  webcoreBinding: RuntimeEnabledFeatures
  category: experimental
  condition: ENABLE(DARK_MODE_CSS)

WebSQLDisabled:
  type: bool
  defaultValue: true
  humanReadableName: "Disable Web SQL"
  humanReadableDescription: "Disable Web SQL"
  webcoreBinding: RuntimeEnabledFeatures
  category: experimental

This one's weird because it's Disabled rather than Enabled... the 
semantics should probably be reversed. We probably want a WebSQLEnabled 
feature defaulting to false?

ProcessSwapOnCrossSiteNavigationEnabled:
  type: bool
  defaultValue: DEFAULT_PROCESS_SWAP_ON_CROSS_SITE_NAVIGATION_ENABLED
  humanReadableName: "Swap Processes on Cross-Site Navigation"
  humanReadableDescription: "Swap WebContent processes on cross-site 
navigations"
  category: experimental
  webcoreBinding: none

DEFAULT_PROCESS_SWAP_ON_CROSS_SITE_NAVIGATION_ENABLED is TRUE on macOS 
and iOS, bypassing DEFAULT_EXPERIMENTAL_FEATURES_ENABLED.