DevTools: add extension API to contribute trace events to timeline

third_party/WebKit/Source/devtools/front_end/timeline/ExtensionTracingSession.js

Index: third_party/WebKit/Source/devtools/front_end/timeline/ExtensionTracingSession.js
diff --git a/third_party/WebKit/Source/devtools/front_end/timeline/ExtensionTracingSession.js b/third_party/WebKit/Source/devtools/front_end/timeline/ExtensionTracingSession.js
new file mode 100644
index 0000000000000000000000000000000000000000..de108a86cfdecd62366182aa31f79dcb9ae6b497
--- /dev/null
+++ b/third_party/WebKit/Source/devtools/front_end/timeline/ExtensionTracingSession.js
@@ -0,0 +1,78 @@
+// Copyright 2016 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 {Extensions.TracingSession}
+ * @implements {Timeline.LoaderClient}
+ */
+Timeline.ExtensionTracingSession = class {
+  /**
+   * @param {!Extensions.ExtensionTraceProvider} provider
+   * @param {!Timeline.TimelineLifecycleDelegate} delegate
+   */
+  constructor(provider, delegate) {
+    this._provider = provider;
+    this._delegate = delegate;
+    this._sessionGeneration = delegate.sessionGeneration();
+    /** @type {function()} */
+    this._completionCallback;
+    this._completionPromise = new Promise(fulfill => {this._completionCallback = fulfill;});
+    /** @type {?SDK.TracingModel} */
+    this._tracingModel = null;
+    /** @type {number} */
+    this._timeOffset = 0;
+  }
+
+  /** @override */
+  loadingStarted() {
+  }
+
+  /**
+   * @override
+   * @param {number=} progress
+   */
+  loadingProgress(progress) {
+  }
+
+  /**
+   * @override
+   * @param {boolean} success
+   */
+  loadingComplete(success) {
+    if (!success || this._sessionGeneration !== this._delegate.sessionGeneration()) {
+      this._tracingModel.reset();
+    } else {
+      this._delegate.addExtensionEvents(
+          this._provider.longDisplayName(),
+          /** @type {!SDK.TracingModel} */ (this._tracingModel), this._timeOffset);
+    }
+    this._completionCallback();
+  }
+
+  /**
+   * @override
+   * @param {string} url
+   * @param {number} timeOffsetMicroseconds
+   */
+  complete(url, timeOffsetMicroseconds) {
+    if (!url || this._sessionGeneration !== this._delegate.sessionGeneration()) {
+      this._completionCallback();
+      return;
+    }
+    var storage = new Bindings.TempFileBackingStorage('tracing');
+    this._tracingModel = new SDK.TracingModel(storage);
+    this._timeOffset = timeOffsetMicroseconds;
+    Timeline.TimelineLoader.loadFromURL(this._tracingModel, url, this);
+  }
+
+  start() {
+    this._provider.start(this);
+  }
+
+  /** @return {!Promise<string>} */
+  stop() {
+    this._provider.stop();
+    return this._completionPromise;
+  }
+};