Browser Plugin: Implement CanGoBack/CanGoForward

content/renderer/browser_plugin/browser_plugin.h

 // Copyright (c) 2012 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  CONTENT_RENDERER_BROWSER_PLUGIN_BROWSER_PLUGIN_H_
 #define  CONTENT_RENDERER_BROWSER_PLUGIN_BROWSER_PLUGIN_H_
 
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebPlugin.h"
 
 #include "base/memory/scoped_ptr.h"
 #include "base/sequenced_task_runner_helpers.h"
 #if defined(OS_WIN)
 #include "base/shared_memory.h"
 #endif
 #include "content/renderer/browser_plugin/browser_plugin_backing_store.h"
 #include "content/renderer/browser_plugin/browser_plugin_bindings.h"
 #include "content/renderer/render_view_impl.h"
 
 struct BrowserPluginHostMsg_ResizeGuest_Params;
+struct BrowserPluginMsg_DidNavigate_Params;
 struct BrowserPluginMsg_UpdateRect_Params;
 
 namespace content {
 
 class BrowserPluginManager;
 class MockBrowserPlugin;
 
 class CONTENT_EXPORT BrowserPlugin :
     NON_EXPORTED_BASE(public WebKit::WebPlugin) {
  public:
   // Called only by tests to clean up before we blow away the MockRenderProcess.
   void Cleanup();
 
   // Get the src attribute value of the BrowserPlugin instance if the guest
   // has not crashed.
   std::string GetSrcAttribute() const;
   // Set the src attribute value of the BrowserPlugin instance and reset
   // the guest_crashed_ flag.
   void SetSrcAttribute(const std::string& src);
   // Returns Chrome's process ID for the current guest.
   int process_id() const { return process_id_; }
   // The partition identifier string is stored as UTF-8.
   std::string GetPartitionAttribute() const;
+  // Query whether the guest can navigate back to the previous entry.
+  bool CanGoBack() const;
+  // Query whether the guest can navigation forward to the next entry.
+  bool CanGoForward() const;
   // This method can be successfully called only before the first navigation for
   // this instance of BrowserPlugin. If an error occurs, the |error_message| is
   // set appropriately to indicate the failure reason.
   bool SetPartitionAttribute(const std::string& partition_id,
                              std::string& error_message);
 
   // Inform the BrowserPlugin to update its backing store with the pixels in
   // its damage buffer.
   void UpdateRect(int message_id,
                   const BrowserPluginMsg_UpdateRect_Params& params);
   // Inform the BrowserPlugin that its guest has crashed.
   void GuestCrashed();
   // Informs the BrowserPlugin that the guest has navigated to a new URL.
-  void DidNavigate(const GURL& url, int process_id);
+  void DidNavigate(const BrowserPluginMsg_DidNavigate_Params& params);
   // Inform the BrowserPlugin that the guest has started loading a new page.
   void LoadStart(const GURL& url, bool is_top_level);
   // Inform the BrowserPlugin that the guest has aborted loading a new page.
   void LoadAbort(const GURL& url, bool is_top_level, const std::string& type);
   // Inform the BrowserPlugin that the guest has redirected a navigation.
   void LoadRedirect(const GURL& old_url,
                     const GURL& new_url,
                     bool is_top_level);
   // Tells the BrowserPlugin to advance the focus to the next (or previous)
   // element.
@@ skipping 126 matching lines @@
   bool persist_storage_;
   // Tracks the visibility of the browser plugin regardless of the whole
   // embedder RenderView's visibility.
   bool visible_;
   typedef std::vector<v8::Persistent<v8::Function> > EventListeners;
   typedef std::map<std::string, EventListeners> EventListenerMap;
   EventListenerMap event_listener_map_;
 #if defined(OS_WIN)
   base::SharedMemory shared_memory_;
 #endif
+  // Important: Do not add more history state here.
+  // We strongly discourage storing additional history state (such as page IDs)
+  // in the embedder process, at the risk of having incorrect information that
+  // can lead to broken back/forward logic in apps.
+  // It's also important that this state does not get modified by any logic in
+  // the embedder process. It should only be updated in response to navigation
+  // events in the guest.  No assumptions should be made about how the index
+  // will change after a navigation (e.g., for back, forward, or go), because
+  // the changes are not always obvious.  For example, there is a maximum
+  // number of entries and earlier ones will automatically be pruned.
+  int current_nav_entry_index_;
+  int nav_entry_count_;
   DISALLOW_COPY_AND_ASSIGN(BrowserPlugin);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_BROWSER_PLUGIN_BROWSER_PLUGIN_H_