Fire remove monitors VM event

src/engine/runtime.js

@@ -241,6 +241,14 @@ class Runtime extends EventEmitter {
         return 'MONITORS_UPDATE';
     }
 
+    /**
+     * Event name for monitors removed.
+     * @const {string}
+     */
+    static get MONITORS_REMOVED () {
+        return 'MONITORS_REMOVED';
+    }
+
     /**
      * How rapidly we try to step threads by default, in ms.
      */
@@ -859,12 +867,20 @@ class Runtime extends EventEmitter {
 
     /**
      * Emit a monitor update which adds or updates if exists the given monitors.
-     * @param {!Array} monitors Array of all monitors
+     * @param {!Array} monitors Array of monitors to update.
      */
     updateMonitors (monitors) {
         this.emit(Runtime.MONITORS_UPDATE, monitors);
     }
 
+    /**
+     * Emit a monitor update which removes if exists the given monitors.
+     * @param {!Array} monitors Array of monitors to remove.
+     */
+    removeMonitors (monitors) {
+        this.emit(Runtime.MONITORS_REMOVED, monitors);
+    }
+
     /**
      * Get a target by its id.
      * @param {string} targetId Id of target to find.