1 files changed, 42 insertions, 0 deletions
diff --git a/devtools/server/actors/resources/css-changes.js b/devtools/server/actors/resources/css-changes.js
new file mode 100644
index 0000000000..ba4d424ffb
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+++ b/devtools/server/actors/resources/css-changes.js
@@ -0,0 +1,42 @@
+/* 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 {
+  TYPES: { CSS_CHANGE },
+} = require("devtools/server/actors/resources/index");
+const TrackChangeEmitter = require("devtools/server/actors/utils/track-change-emitter");
+
+/**
+ * Start watching for all css changes related to a given Target Actor.
+ *
+ * @param TargetActor targetActor
+ *        The target actor from which we should observe css changes.
+ * @param Object options
+ *        Dictionary object with following attributes:
+ *        - onAvailable: mandatory function
+ *          This will be called for each resource.
+ */
+class CSSChangeWatcher {
+  constructor() {
+    this.onTrackChange = this.onTrackChange.bind(this);
+  }
+
+  async watch(targetActor, { onAvailable }) {
+    this.onAvailable = onAvailable;
+    TrackChangeEmitter.on("track-change", this.onTrackChange);
+  }
+
+  onTrackChange(change) {
+    change.resourceType = CSS_CHANGE;
+    this.onAvailable([change]);
+  }
+
+  destroy() {
+    TrackChangeEmitter.off("track-change", this.onTrackChange);
+  }
+}
+
+module.exports = CSSChangeWatcher;