[TooManyTabs] Add TabNavigationThrottle

chrome/browser/resource_coordinator/tab_navigation_throttle.h

+// 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.
+
+#ifndef CHROME_BROWSER_RESOURCE_COORDINATOR_TAB_NAVIGATION_THROTTLE_H_
+#define CHROME_BROWSER_RESOURCE_COORDINATOR_TAB_NAVIGATION_THROTTLE_H_
+
+#include <memory>
+
+#include "base/macros.h"
+#include "content/public/browser/navigation_throttle.h"
+
+namespace resource_coordinator {
+
+// TabNavigationThrottle plumbs navigation information to TabManager and enables
+// TabManager to control navigation for background tabs.

[Charlie Reis, 2017/06/10 00:53:36]

Can you elaborate on this a bit more?  "Controlling navigation" sounds broad,
but this is just about delaying navigations to reduce contention.

[Zhen Wang, 2017/06/13 23:33:21]

I replaced "control" with "delay". We indeed just consider delaying the
navigation.

+class TabNavigationThrottle : public content::NavigationThrottle {

[Charlie Reis, 2017/06/10 00:53:36]

This name seems too broad, since most navigation throttles are about navigations
in tabs.  Would BackgroundTabNavigationThrottle be more accurate?

[Zhen Wang, 2017/06/13 23:33:21]

SG. Renamed.

+ public:
+  static std::unique_ptr<TabNavigationThrottle> MaybeCreateThrottleFor(
+      content::NavigationHandle* navigation_handle);
+
+  explicit TabNavigationThrottle(content::NavigationHandle* navigation_handle);
+  ~TabNavigationThrottle() override;
+
+  // content::NavigationThrottle implementation
+  const char* GetNameForLogging() override;
+  content::NavigationThrottle::ThrottleCheckResult WillStartRequest() override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TabNavigationThrottle);
+};
+
+}  // namespace resource_coordinator
+
+#endif  // CHROME_BROWSER_RESOURCE_COORDINATOR_TAB_NAVIGATION_THROTTLE_H_