Bug 1696776 - Expose socket transport in TCPSocket. r=valentin

Same deal, Thunderbird could really use this.

Differential Revision: https://phabricator.services.mozilla.com/D107380

dom/bindings/Bindings.conf

@@ -1926,6 +1926,8 @@ addExternalIface('nsIPrintSettings', nativeType='nsIPrintSettings',
                  notflattened=True)
 addExternalIface('nsISelectionListener', nativeType='nsISelectionListener')
 addExternalIface('nsIStreamListener', nativeType='nsIStreamListener', notflattened=True)
+addExternalIface('nsISocketTransport', nativeType='nsISocketTransport',
+                 notflattened=True)
 addExternalIface('nsITransportProvider', nativeType='nsITransportProvider')
 addExternalIface('nsITreeSelection', nativeType='nsITreeSelection',
                  notflattened=True)

dom/network/TCPSocket.h

@@ -93,6 +93,8 @@ class TCPSocket final : public DOMEventTargetHelper,
 
   static bool ShouldTCPSocketExist(JSContext* aCx, JSObject* aGlobal);
 
+  nsISocketTransport* GetTransport() const { return mTransport.get(); }
+
   void GetHost(nsAString& aHost);
   uint32_t Port();
   bool Ssl();

dom/webidl/TCPSocket.webidl

@@ -10,6 +10,8 @@
  * event handler based interface.
  */
 
+interface nsISocketTransport;
+
 enum TCPSocketBinaryType {
   "arraybuffer",
   "string"
@@ -52,6 +54,11 @@ interface TCPSocket : EventTarget {
    */
   [Throws] void upgradeToSecure();
 
+  /**
+   * The raw internal socket transport.
+   */
+  readonly attribute nsISocketTransport? transport;
+
   /**
    * The UTF16 host of this socket object.
    */