[WebDriver][BiDi] Support session.new to create BiDi-only sessions - #75992

[WebDriver][BiDi] Support session.new to create BiDi-only sessions
https://bugs.webkit.org/show_bug.cgi?id=281722

Reviewed by NOBODY (OOPS!).

Depends on #77457.
Upstream WPT coverage: web-platform-tests/wpt#63552

Handle session.new as a static WebDriverService command. Reuse the existing
session-creation pipeline in BiDi-only mode, build the required BiDi
capabilities result, and associate the requesting WebSocket before replying.

Reserve the single session slot across asynchronous HTTP and BiDi creation so
overlapping requests cannot create multiple sessions. Validate capabilities
before reporting that the slot is unavailable, consistently returning invalid
argument for malformed HTTP and BiDi capability requests. Report automation-
session startup failures as session not created, close provisional sessions
after later creation failures, and keep sessions created through BiDi
inaccessible to classic HTTP commands.

Keep --replace-on-new-session protocol-independent. When enabled, a classic
HTTP new-session request may replace an existing BiDi-only session. Reserve the
shared session slot before detaching the old session so another creation cannot
claim the temporary gap.

Make session startup and the service-level creation finalizer one-shot. Complete
a pending startup when the inspector disconnects or a locally launched browser
exits before establishing its inspector connection. This ensures every
terminal path releases the in-progress session reservation and replies once.

Cancel an in-progress BiDi session creation when its initiating WebSocket
disconnects, releasing the reservation without attempting to reply on the dead
connection. When an active browser terminates, detach only the session whose ID
matches the termination notification before cleaning up its WebSocket mapping,
so replacement capacity is restored without exposing a newer session to stale
cleanup.

Register a reconnect resource for a successfully created BiDi-only session.
Closing its transport does not end the session, so a client can reconnect to
the same session ID. Remove the resource and connection mapping during
definitive teardown. Revalidate resource ownership in the delayed
post-handshake callback so teardown racing an accepted upgrade cannot attach a
new connection to an ended session.

Defer browser.close termination to the next main-run-loop turn. This lets the
generated BiDi dispatcher send the command's empty success response before
automation-session cleanup disconnects the inspector channel.

Return the user agent applied by WebPageProxy with the initial browsing-context
response. Store that value in the session capabilities and use it directly in
the BiDi result, avoiding a second backend command and page-visible
navigator.userAgent evaluation.

• Source/WebDriver/Session.cpp:
  (WebDriver::Session::Session): Record whether the session is addressable
  through classic HTTP.
  (WebDriver::Session::createTopLevelBrowsingContext): Store the applied user
  agent returned with the initial context for BiDi session capabilities.
• Source/WebDriver/Session.h:
  Expose the HTTP flag used by BiDi session creation.
• Source/WebDriver/Capabilities.h:
  Store the applied user agent used by a BiDi session result.
• Source/WebDriver/SessionHost.cpp:
  (WebDriver::SessionHost::completeStartAutomationSession): Added. Consume the
  pending startup completion from one common terminal path.
  (WebDriver::SessionHost::inspectorDisconnected): Fail a pending startup when
  the inspector connection closes.
• Source/WebDriver/SessionHost.h:
  Use CompletionHandler for automation-session startup, store it for all
  platform implementations, expose creation cancellation, and retain the
  authoritative user agent in the session capabilities.
• Source/WebDriver/WebDriverService.cpp:
  (WebDriver::WebDriverService::s_staticBidiCommands): Register session.new.
  (WebDriver::WebDriverService::handleRequest): Reject classic commands targeting
  a BiDi-only session.
  (WebDriver::WebDriverService::acceptHandshake): Reject a second active
  connection for the same session.
  (WebDriver::WebDriverService::handleMessage): Pass the initiating connection to
  static command handlers.
  (WebDriver::WebDriverService::newSession): Reserve the shared session slot
  during asynchronous HTTP creation.
  (WebDriver::WebDriverService::connectToBrowser): Propagate the creation mode and
  provisional session result.
  (WebDriver::WebDriverService::createSession): Share session startup between HTTP
  and BiDi, report startup failures as session not created, and clean up failed
  provisional sessions.
  (WebDriver::WebDriverService::buildBidiSessionResult): Added.
  (WebDriver::WebDriverService::status): Report an in-progress creation as
  unavailable.
  (WebDriver::WebDriverService::bidiSessionNew): Add BiDi-only session creation
  and validate capabilities before checking session capacity.
  (WebDriver::WebDriverService::bidiSessionStatus): Account for an in-progress
  creation.
  (WebDriver::WebDriverService::clientDisconnected): Cancel session creation
  owned by the disconnected WebSocket.
  (WebDriver::WebDriverService::onBrowserTerminated): Release the matching active
  session before disconnecting its WebSocket mapping.
• Source/WebDriver/WebDriverService.h:
  (WebDriver::WebDriverService::SessionCreationMode): Name the classic WebDriver
  and BiDi session-creation paths.
  Declare the shared creation state and handlers. Use CompletionHandler for the
  terminal session-creation callback.
• Source/WebDriver/WebSocketServer.cpp:
  (WebDriver::WebSocketServer::associateConnectionWithSession): Added.
  (WebDriver::WebSocketServer::addConnection): Revalidate reconnect-resource
  ownership and connection uniqueness immediately before inserting a
  post-handshake connection mapping.
  (WebDriver::WebSocketServer::startListening): Register session resources
  idempotently.
• Source/WebDriver/WebSocketServer.h:
  Declare atomic association of an unassociated connection with a session and
  report whether a post-handshake connection was registered.
• Source/WebDriver/glib/SessionHostGlib.cpp:
  (WebDriver::SessionHost::connectToBrowser): Complete with an error if the
  launched browser exits before its inspector connection is established, and
  complete cancelled connection attempts.
  (WebDriver::SessionHost::cancelSessionCreation): Added.
  (WebDriver::SessionHost::startAutomationSession): Store the one-shot startup
  completion.
  (WebDriver::SessionHost::didStartAutomationSession): Use the common completion
  path after a capability mismatch.
  (WebDriver::SessionHost::setTargetList): Use the common completion path after
  successful startup.
• Source/WebDriver/socket/SessionHostSocket.cpp:
  (WebDriver::SessionHost::cancelSessionCreation): Added.
  (WebDriver::SessionHost::startAutomationSession): Store the one-shot startup
  completion.
  (WebDriver::SessionHost::setTargetList): Route disconnect and success through
  the common completion paths.
• Source/WebDriver/soup/WebSocketServerSoup.cpp:
  (WebDriver::handleWebSocketConnection): Close connections that lose session
  ownership during the handshake callback gap.
  (WebDriver::WebSocketServer::disconnectSession): Remove the reconnect resource
  and mapping synchronously before closing the socket.
• Source/WebKit/UIProcess/Automation/BidiBrowserAgent.cpp:
  (WebKit::BidiBrowserAgent::close): Schedule session termination after the
  generated success response has been sent.
• Source/WebKit/UIProcess/Automation/BidiBrowsingContextAgent.cpp:
  (WebKit::BidiBrowsingContextAgent::create): Accept the user agent added to the
  shared browsing-context response while returning the context identifier.
• Source/WebKit/UIProcess/Automation/Automation.json:
  Add the applied user agent to the createBrowsingContext result.
• Source/WebKit/UIProcess/Automation/WebAutomationSession.cpp:
  (WebKit::WebAutomationSession::createBrowsingContext): Return
  WebPageProxy::userAgent() with the newly created context.
• Source/WebKit/UIProcess/Automation/WebAutomationSession.h:
  Update the generated createBrowsingContext callback signature.
• Tools/TestWebKitAPI/Tests/WebKit/WKWebView/glib/TestAutomationSession.cpp:
  Verify that createBrowsingContext returns the configured WebKit user agent.

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