Creates BrowserTabStripTracker to consolidate common code

chrome/browser/ui/browser_tab_strip_tracker.h

Index: chrome/browser/ui/browser_tab_strip_tracker.h
diff --git a/chrome/browser/ui/browser_tab_strip_tracker.h b/chrome/browser/ui/browser_tab_strip_tracker.h
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+// Copyright 2015 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_UI_BROWSER_TAB_STRIP_TRACKER_H_
+#define CHROME_BROWSER_UI_BROWSER_TAB_STRIP_TRACKER_H_
+
+#include <set>
+
+#include "base/basictypes.h"
+#include "chrome/browser/ui/browser_list_observer.h"
+
+class BrowserTabStripTrackerDelegate;
+class TabStripModelObserver;
+
+// BrowserTabStripTracker is useful when you want to attach a
+// TabStripModelObserver to a subset of the available browsers, as well as
+// tracking new Browsers as they are added.
+//
+// To constrain the set of Browsers to track use a
+// BrowserTabStripTrackerDelegate. BrowserTabStripTracker queries the delegate
+// for each Browser to determine if the Browser should be tracked. A null
+// delegate indicates all Browsers should be observed.
+//
+// If you are interested in BrowserListObserver functions specify a
+// BrowserListObserver in the constructor. OnBrowserAdded() and
+// OnBrowserRemoved() are only called if the delegate indicates the browser
+// should be tracked.
+class BrowserTabStripTracker : public chrome::BrowserListObserver {
+ public:
+  // See Init() for details.
+  enum class InitWith {
+    BROWSERS_IN_ACTIVE_DESKTOP,
+    ALL_BROWERS,
+  };
+
+  // See class description for details. You only need specify a
+  // TabStripModelObserver. |delegate| and |browser_list_observer| are
+  // optional.
+  BrowserTabStripTracker(TabStripModelObserver* tab_strip_model_observer,
+                         BrowserTabStripTrackerDelegate* delegate,
+                         BrowserListObserver* browser_list_observer);
+  ~BrowserTabStripTracker() override;
+
+  // Starts tracking BrowserList for changes and additionally observes the
+  // existing Browsers matching |init_with|. If there is a
+  // BrowserTabStripTrackerDelegate it is called to determine if the Browser
+  // should be observed. If an existing Browser should be observed
+  // TabInsertedAt() is called for any existing tabs. If a delegate needs to
+  // differentiate between Browsers observed by way of Init() vs. a Browser
+  // added after the fact use is_processing_initial_browsers().
+  void Init(InitWith init_with);
+
+  // Returns true if processing an existing Browser in Init().
+  bool is_processing_initial_browsers() const {
+    return is_processing_initial_browsers_;
+  }
+
+  // Stops observing the current set of observed browsers and calls
+  // BrowserListObserver::OnBrowserRemoved().
+  void StopObservingAndSendOnBrowserRemoved();
+
+ private:
+  using Browsers = std::set<Browser*>;
+
+  // Returns true if a TabStripModelObserver should be added to |browser|.
+  bool ShouldTrackBrowser(Browser* browser);
+
+  // If ShouldTrackBrowser() returns true for |browser| then a
+  // TabStripModelObserver is attached.
+  void MaybeTrackBrowser(Browser* browser);
+
+  // BrowserListObserver:
+  void OnBrowserAdded(Browser* browser) override;
+  void OnBrowserRemoved(Browser* browser) override;
+  void OnBrowserSetLastActive(Browser* browser) override;
+
+  TabStripModelObserver* tab_strip_model_observer_;
+  BrowserTabStripTrackerDelegate* delegate_;
+  BrowserListObserver* browser_list_observer_;
+  bool is_processing_initial_browsers_;
+  Browsers browsers_observing_;
+
+  DISALLOW_COPY_AND_ASSIGN(BrowserTabStripTracker);
+};
+
+#endif  // CHROME_BROWSER_UI_BROWSER_TAB_STRIP_TRACKER_H_