DevTools: make cpu throttling manager a control factory we can reuse.

third_party/WebKit/Source/devtools/front_end/components/CPUThrottlingManager.js

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * @implements {SDK.TargetManager.Observer}
+ */
+Components.CPUThrottlingManager = class extends Common.Object {
+  constructor() {
+    super();
+    this._throttlingRate = 1;  // No throttling
+    SDK.targetManager.observeTargets(this, SDK.Target.Capability.Browser);
+    /** @type {!Set<!UI.ToolbarComboBox>} */
+    this._controls = new Set();
+    this._rates = [1, 2, 5, 10, 20];
+  }
+
+  /**
+   * @param {number} index
+   */
+  _setRateIndex(index) {
+    this._throttlingRate = this._rates[index];
+    SDK.targetManager.targets().forEach(target => target.emulationAgent().setCPUThrottlingRate(this._throttlingRate));
+    var icon = null;
+    if (this._throttlingRate !== 1) {
+      icon = UI.Icon.create('smallicon-warning');
+      icon.title = Common.UIString('CPU throttling is enabled');
+    }
+    for (var control of this._controls)
+      control.setSelectedIndex(index);
+    UI.inspectorView.setPanelIcon('timeline', icon);
+    this.dispatchEventToListeners(Components.CPUThrottlingManager.Events.RateChanged);
+  }
+
+  /**
+   * @return {number}
+   */
+  rate() {
+    return this._throttlingRate;
+  }
+
+  /**
+   * @override
+   * @param {!SDK.Target} target
+   */
+  targetAdded(target) {

[dgozman, 2017/01/13 03:03:18]

This goes against our common scheme, which would be:
- CPUThrottlingModel talking to agents, having rate(), setRate() and RateChanged
event.
- CPUThrottlingSelector which listens to the model and calls methods on it.

+    if (this._throttlingRate !== 1)
+      target.emulationAgent().setCPUThrottlingRate(this._throttlingRate);
+  }
+
+  /**
+   * @override
+   * @param {!SDK.Target} target
+   */
+  targetRemoved(target) {
+  }
+
+  /**
+   * @return {!UI.ToolbarComboBox}
+   */
+  createControl() {
+    var control = new UI.ToolbarComboBox(event => this._setRateIndex(event.target.selectedIndex));
+    this._controls.add(control);
+    var currentRate = this._throttlingRate;
+
+    for (var i = 0; i < this._rates.length; ++i) {
+      var rate = this._rates[i];
+      var title = rate === 1 ? Common.UIString('No throttling') : Common.UIString('%d\xD7 slowdown', rate);
+      var option = control.createOption(title);
+      control.addOption(option);
+      if (currentRate === rate)
+        control.setSelectedIndex(i);
+    }
+    return control;
+  }
+
+  /**
+   * @param {!UI.ToolbarComboBox} control
+   */
+  disposeControl(control) {
+    this._controls.delete(control);
+  }
+};
+
+/** @enum {symbol} */
+Components.CPUThrottlingManager.Events = {
+  RateChanged: Symbol('RateChanged')
+};