Revert of Make profiling lock global rather than per Target

Source/devtools/front_end/timeline/TimelinePanel.js

Index: Source/devtools/front_end/timeline/TimelinePanel.js
diff --git a/Source/devtools/front_end/timeline/TimelinePanel.js b/Source/devtools/front_end/timeline/TimelinePanel.js
index 0728cd94ab462577db696a1eb389342556351bd9..f2c242f0c2a0bc6ae050e58c2f654d6d5d9fc811 100644
--- a/Source/devtools/front_end/timeline/TimelinePanel.js
+++ b/Source/devtools/front_end/timeline/TimelinePanel.js
@@ -34,6 +34,7 @@
  * @extends {WebInspector.Panel}
  * @implements {WebInspector.TimelineModeViewDelegate}
  * @implements {WebInspector.Searchable}
+ * @implements {WebInspector.TargetManager.Observer}
  */
 WebInspector.TimelinePanel = function()
 {
@@ -123,7 +124,6 @@
 
     this._onModeChanged();
     this._detailsSplitView.show(this.element);
-    WebInspector.profilingLock.addEventListener(WebInspector.Lock.Events.StateChanged, this._onProfilingStateChanged, this);
 }
 
 WebInspector.TimelinePanel.OverviewMode = {
@@ -138,6 +138,22 @@
 WebInspector.TimelinePanel.durationFilterPresetsMs = [0, 1, 15];
 
 WebInspector.TimelinePanel.prototype = {
+    /**
+     * @param {!WebInspector.Target} target
+     */
+    targetAdded: function(target)
+    {
+        target.profilingLock.addEventListener(WebInspector.Lock.Events.StateChanged, this._onProfilingStateChanged, this);
+    },
+
+    /**
+     * @param {!WebInspector.Target} target
+     */
+    targetRemoved: function(target)
+    {
+        target.profilingLock.removeEventListener(WebInspector.Lock.Events.StateChanged, this._onProfilingStateChanged, this);
+    },
+
     /**
      * @return {?WebInspector.SearchableView}
      */
@@ -674,7 +690,7 @@
      */
     _updateToggleTimelineButton: function(toggled)
     {
-        var isAcquiredInSomeTarget = WebInspector.profilingLock.isAcquired();
+        var isAcquiredInSomeTarget = WebInspector.targetManager.targets().some(function(target) { return target.profilingLock.isAcquired(); });
         this.toggleTimelineButton.toggled = toggled;
         if (toggled) {
             this.toggleTimelineButton.title = WebInspector.UIString("Stop");