[DevTools] Turn TracingManager into SDKModel.

third_party/WebKit/Source/devtools/front_end/sdk/TracingManager.js

Index: third_party/WebKit/Source/devtools/front_end/sdk/TracingManager.js
diff --git a/third_party/WebKit/Source/devtools/front_end/sdk/TracingManager.js b/third_party/WebKit/Source/devtools/front_end/sdk/TracingManager.js
index 06f4e03ecfbe69b35b411b5f24b1eae53538838d..9e7af8e8046bcdcc18a2e1cd2ac61f864f708e0a 100644
--- a/third_party/WebKit/Source/devtools/front_end/sdk/TracingManager.js
+++ b/third_party/WebKit/Source/devtools/front_end/sdk/TracingManager.js
@@ -27,12 +27,13 @@ SDK.TracingManagerClient.prototype = {
 /**
  * @unrestricted
  */
-SDK.TracingManager = class {
+SDK.TracingManager = class extends SDK.SDKModel {
   /**
    * @param {!SDK.Target} target
    */
   constructor(target) {
-    this._target = target;
+    super(target);
+    this._tracingAgent = target.tracingAgent();
     target.registerTracingDispatcher(new SDK.TracingDispatcher(this));
 
     /** @type {?SDK.TracingManagerClient} */
@@ -42,13 +43,6 @@ SDK.TracingManager = class {
   }
 
   /**
-   * @return {?SDK.Target}
-   */
-  target() {
-    return this._target;
-  }
-
-  /**
    * @param {number=} usage
    * @param {number=} eventCount
    * @param {number=} percentFull
@@ -90,7 +84,7 @@ SDK.TracingManager = class {
       throw new Error('Tracing is already started');
     var bufferUsageReportingIntervalMs = 500;
     this._activeClient = client;
-    return this._target.tracingAgent().start(
+    return this._tracingAgent.start(
         categoryFilter, options, bufferUsageReportingIntervalMs, SDK.TracingManager.TransferMode.ReportEvents);
   }
 
@@ -100,10 +94,12 @@ SDK.TracingManager = class {
     if (this._finishing)
       throw new Error('Tracing is already being stopped');
     this._finishing = true;
-    this._target.tracingAgent().end();
+    this._tracingAgent.end();
   }
 };
 
+SDK.SDKModel.register(SDK.TracingManager, SDK.Target.Capability.Tracing);
+
 /** @typedef {!{
         cat: string,
         pid: number,