Restrict number of BlimpContents to [0, 1]

blimp/client/core/contents/blimp_contents_manager.h

 // 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.
 
 #ifndef BLIMP_CLIENT_CORE_CONTENTS_BLIMP_CONTENTS_MANAGER_H_
 #define BLIMP_CLIENT_CORE_CONTENTS_BLIMP_CONTENTS_MANAGER_H_
 
 #include "blimp/client/core/contents/blimp_contents_impl.h"
 
 namespace blimp {
 namespace client {
 
 class TabControlFeature;
 
 // BlimpContentsManager does the real work of creating BlimpContentsImpl, and
 // then passes the ownership to the caller. It also owns the observers to
 // monitor the life time of the contents it creates.
 class BlimpContentsManager {
  public:
   explicit BlimpContentsManager(ImeFeature* ime_feature,
                                 NavigationFeature* nav_feature,
                                 TabControlFeature* tab_control_feature);
   ~BlimpContentsManager();
 
   // Builds a BlimpContentsImpl and notifies the engine.
+  // Currently we want to have a single BlimpContents. If there is an existing
+  // contents, return nullptr.
   std::unique_ptr<BlimpContentsImpl> CreateBlimpContents();
 
   // The caller can query the contents through its id.
   BlimpContentsImpl* GetBlimpContents(int id);
 
  private:
   class BlimpContentsDeletionObserver;
   friend class BlimpContentsDeletionObserver;
 
   // When creating the BlimpContentsImpl, an id is created for the content.
@@ skipping 12 matching lines @@
 
   // BlimpContentsManager owns the BlimpContentsDeletionObserver for the
   // contents it creates, with the content id being the key to help manage the
   // lifetime of the observers.
   std::map<int, std::unique_ptr<BlimpContentsDeletionObserver>> observer_map_;
 
   ImeFeature* ime_feature_;
   NavigationFeature* navigation_feature_;
   TabControlFeature* tab_control_feature_;
 
+  // TODO(mlliu): Currently we want to have a single BlimpContents. Remove this
+  // when it supports multiple tabs.
+  bool tab_exists_ = false;

[David Trainor- moved to gerrit, 2016/08/30 23:31:12]

Can we just check the map to see if any entries exist?

[Menglin, 2016/08/31 00:13:02]

There can be such case:
https://codesearch.chromium.org/chromium/src/blimp/client/core/contents/blimp...
, i.e., the contents is destroyed but the observer map is not empty yet. So I
figured it's more straightforward to just use a bool.

+
   base::WeakPtrFactory<BlimpContentsManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BlimpContentsManager);
 };
 
 }  // namespace client
 }  // namespace blimp
 
 #endif  // BLIMP_CLIENT_CORE_CONTENTS_BLIMP_CONTENTS_MANAGER_H_