Bug 1468754 Part 3: Add a TrackChangesEmitter helper object, and make ChangesActor listen to it. r=pbro

Depends on D9049

Differential Revision: https://phabricator.services.mozilla.com/D9050

--HG--
extra : moz-landing-system : lando

devtools/server/actors/styles.js

@@ -9,6 +9,7 @@ const protocol = require("devtools/shared/protocol");
 const {getCSSLexer} = require("devtools/shared/css/lexer");
 const {LongStringActor} = require("devtools/server/actors/string");
 const InspectorUtils = require("InspectorUtils");
+const TrackChangeEmitter = require("devtools/server/actors/utils/track-change-emitter");
 
 // This will also add the "stylesheet" actor type for protocol.js to recognize
 
@@ -1520,7 +1521,7 @@ var StyleRuleActor = protocol.ActorClassWithSpec(styleRuleSpec, {
       return;
     }
 
-    this.emit("track-change", data);
+    TrackChangeEmitter.trackChange(data);
   },
 
   /**

devtools/server/actors/utils/moz.build

@@ -21,5 +21,6 @@ DevToolsModules(
     'source-actor-store.js',
     'stack.js',
     'TabSources.js',
+    'track-change-emitter.js',
     'walker-search.js',
 )

devtools/server/actors/utils/track-change-emitter.js

@@ -0,0 +1,26 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const EventEmitter = require("devtools/shared/event-emitter");
+
+/**
+ * A helper class that is listened to by the ChangesActor, and can be
+ * used to send changes to the ChangesActor.
+ */
+class TrackChangeEmitter {
+  /**
+   * Initialize this object.
+   */
+  constructor() {
+    EventEmitter.decorate(this);
+  }
+
+  trackChange(change) {
+    this.emit("track-change", change);
+  }
+}
+
+module.exports = new TrackChangeEmitter();