Add an unimplemented history API to WebView

Source/web/WebFrameImpl.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 2196 matching lines @@
     // it is necessary to check the value after calling init() and
     // return without loading URL.
     // NOTE: m_client will be null if this frame has been detached.
     // (b:791612)
     childFrame->init(); // create an empty document
     if (!childFrame->tree().parent())
         return nullptr;
 
     // If we're moving in the back/forward list, we might want to replace the content
     // of this child frame with whatever was there at that point.
-    HistoryItem* childItem = 0;
-    if (isBackForwardLoadType(frame()->loader().loadType()) && !frame()->document()->loadEventFinished())
-        childItem = frame()->page()->historyController().itemForNewChildFrame(childFrame.get());
+    RefPtr<HistoryItem> childItem;
+    if (isBackForwardLoadType(frame()->loader().loadType()) && !frame()->document()->loadEventFinished()) {
+        childItem = PassRefPtr<HistoryItem>(webframe->client()->historyItemForNewChildFrame(webframe));
+        if (!childItem)
+            childItem = frame()->page()->historyController().itemForNewChildFrame(childFrame.get());
+    }
 
     if (childItem)
-        childFrame->loader().loadHistoryItem(childItem);
+        childFrame->loader().loadHistoryItem(childItem.get());
     else
         childFrame->loader().load(FrameLoadRequest(0, request.resourceRequest(), "_self"));
 
     // A synchronous navigation (about:blank) would have already processed
     // onload, so it is possible for the frame to have already been destroyed by
     // script in the page.
     // NOTE: m_client will be null if this frame has been detached.
     if (!childFrame->tree().parent())
         return nullptr;
 
@@ skipping 302 matching lines @@
 
         // There is a possibility that the frame being detached was the only
         // pending one. We need to make sure final replies can be sent.
         flushCurrentScopingEffort(m_findRequestIdentifier);
 
         cancelPendingScopingEffort();
     }
 }
 
 } // namespace blink