Task Manager should listen to WebContentsObserver::RenderFrameCreated.

content/public/browser/render_process_host_utils.cc

+// 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.
+
+#include "content/public/browser/render_process_host_utils.h"
+
+#include "base/bind.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/sequenced_task_runner.h"
+#include "base/threading/sequenced_task_runner_handle.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/render_process_host.h"
+#include "content/public/browser/render_process_host_observer.h"
+
+namespace content {
+
+namespace {
+
+class RenderProcessHostIsReadyObserver : public RenderProcessHostObserver {
+ public:
+  RenderProcessHostIsReadyObserver(RenderProcessHost* render_process_host,
+                                   base::OnceClosure task)
+      : render_process_host_(render_process_host),
+        task_(std::move(task)),
+        weak_factory_(this) {
+    render_process_host_->AddObserver(this);
+    if (render_process_host_->IsReady())
+      PostTask();
+  }
+
+  ~RenderProcessHostIsReadyObserver() override {
+    render_process_host_->RemoveObserver(this);
+  }
+
+  void RenderProcessReady(RenderProcessHost* host) override { PostTask(); }
+
+  void RenderProcessHostDestroyed(RenderProcessHost* host) override {
+    delete this;
+  }
+
+ private:
+  void PostTask() {
+    BrowserThread::PostTask(
+        BrowserThread::UI, FROM_HERE,
+        base::Bind(&RenderProcessHostIsReadyObserver::CallTask,
+                   weak_factory_.GetWeakPtr()));
+  }
+
+  void CallTask() {
+    DCHECK_CURRENTLY_ON(BrowserThread::UI);
+    if (render_process_host_->IsReady()) {
+      std::move(task_).Run();
+      delete this;
+    }
+  }
+
+  RenderProcessHost* render_process_host_;
+  base::OnceClosure task_;
+  base::WeakPtrFactory<RenderProcessHostIsReadyObserver> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(RenderProcessHostIsReadyObserver);
+};
+
+}  // namespace
+
+void PostTaskWhenRenderProcessHostIsReady(
+    RenderProcessHost* render_process_host,
+    base::OnceClosure task) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  DCHECK(render_process_host);
+  DCHECK(!task.is_null());
+  new RenderProcessHostIsReadyObserver(render_process_host, std::move(task));
+}
+
+}  // namespace content