[sync] WebContentsObserver based sessions notifications

chrome/browser/sync/sessions/browser_list_router_helper.h

Index: chrome/browser/sync/sessions/browser_list_router_helper.h
diff --git a/chrome/browser/sync/sessions/browser_list_router_helper.h b/chrome/browser/sync/sessions/browser_list_router_helper.h
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+++ b/chrome/browser/sync/sessions/browser_list_router_helper.h
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+// 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_SYNC_SESSIONS_BROWSER_LIST_ROUTER_HELPER_H_
+#define CHROME_BROWSER_SYNC_SESSIONS_BROWSER_LIST_ROUTER_HELPER_H_
+
+#include "chrome/browser/sync/sessions/sync_sessions_web_contents_router.h"
+#include "chrome/browser/ui/browser_list_observer.h"
+#include "chrome/browser/ui/tabs/tab_strip_model_observer.h"
+
+namespace sync_sessions {
+
+// Non-android helper of SyncSessionsWebContentsRouter that adds tracking for
+// multi-window scenarios(e.g. tab movement between windows). Android doesn't
+// have a BrowserList or TabStrip, so it doesn't compile the needed
+// dependencies, nor would it benefit from the added tracking.
+class BrowserListRouterHelper : public chrome::BrowserListObserver,
+                                public TabStripModelObserver {
+ public:
+  explicit BrowserListRouterHelper(SyncSessionsWebContentsRouter* router);
+  ~BrowserListRouterHelper() override;
+
+ private:
+  // chrome::BrowserListObserver implementation.
+  void OnBrowserAdded(Browser* browser) override;
+  void OnBrowserRemoved(Browser* browser) override;
+  // TabStripModelObserver implementation.
+  void TabInsertedAt(TabStripModel* model,
+                     content::WebContents* web_contents,
+                     int index,
+                     bool foreground) override;
+
+  // |router_| owns |this|.
+  SyncSessionsWebContentsRouter* router_;
+
+  DISALLOW_COPY_AND_ASSIGN(BrowserListRouterHelper);
+};
+
+}  // namespace sync_sessions
+
+#endif  // CHROME_BROWSER_SYNC_SESSIONS_BROWSER_LIST_ROUTER_HELPER_H_