Bug 1719505 - [remote] Add Remote Agent class for content processes. r=webdriver-reviewers,jdescottes

When accessing the nsIRemoteAgent interface from a content
process the running state cannot be determined without
communicating with the Remote Agent class from the parent
process.

Similar to Marionette this patch adds a dedicated class of
the Remote Agent for content processes, and exports an
instance of the appropriate class depending on in which
process the Remote Agent gets created in.

Differential Revision: https://phabricator.services.mozilla.com/D144983

remote/components/RemoteAgent.jsm

@@ -38,7 +38,10 @@ const DEFAULT_PORT = 9222;
 // By default force local connections only
 const LOOPBACKS = ["localhost", "127.0.0.1", "[::1]"];
 
-class RemoteAgentClass {
+const isRemote =
+  Services.appinfo.processType == Services.appinfo.PROCESS_TYPE_CONTENT;
+
+class RemoteAgentParentProcess {
   #allowHosts;
   #allowOrigins;
   #classID;
@@ -62,6 +65,8 @@ class RemoteAgentClass {
     // Supported protocols
     this.#cdp = null;
     this.#webDriverBiDi = null;
+
+    Services.ppmm.addMessageListener("RemoteAgent:IsRunning", this);
   }
 
   get allowHosts() {
@@ -370,6 +375,17 @@ class RemoteAgentClass {
     }
   }
 
+  receiveMessage({ name }) {
+    switch (name) {
+      case "RemoteAgent:IsRunning":
+        return this.running;
+
+      default:
+        logger.warn("Unknown IPC message to parent process: " + name);
+        return null;
+    }
+  }
+
   // XPCOM
 
   get classID() {
@@ -393,7 +409,33 @@ class RemoteAgentClass {
   }
 }
 
-var RemoteAgent = new RemoteAgentClass();
+class RemoteAgentContentProcess {
+  #classID;
+
+  constructor() {
+    this.#classID = Components.ID("{8f685a9d-8181-46d6-a71d-869289099c6d}");
+  }
+
+  get running() {
+    let reply = Services.cpmm.sendSyncMessage("RemoteAgent:IsRunning");
+    if (reply.length == 0) {
+      logger.warn("No reply from parent process");
+      return false;
+    }
+    return reply[0];
+  }
+
+  get QueryInterface() {
+    return ChromeUtils.generateQI(["nsIRemoteAgent"]);
+  }
+}
+
+var RemoteAgent;
+if (isRemote) {
+  RemoteAgent = new RemoteAgentContentProcess();
+} else {
+  RemoteAgent = new RemoteAgentParentProcess();
+}
 
 // This is used by the XPCOM codepath which expects a constructor
 var RemoteAgentFactory = function() {

remote/doc/cdp/Architecture.md

@@ -48,8 +48,7 @@ To do that this component glue together three main high level components:
 Connecting to Websocket endpoints
 ---------------------------------
 
-Each target's websocket URL will be registered as a HTTP endpoint via `server/HTTPD:registerPathHandler`.
-(This registration is done from `RemoteAgentClass:listen`)
+Each target's websocket URL will be registered as a HTTP endpoint via `server/HTTPD:registerPathHandler` (This registration is done from `RemoteAgentParentProcess:#listen`).
 Once a HTTP request happens, `server/HTTPD` will call the `handle` method on the object passed to `registerPathHandler`.
 For static endpoints registered by `JSONHandler`, this will call `JSONHandler:handle` and return a JSON string as http body.
 For target's endpoint, it is slightly more complicated as it requires a special handshake to morph the HTTP connection into a WebSocket one.