Remove BackForwardClient, cleanup starting a history navigation

Source/web/FrameLoaderClientImpl.cpp

 /*
  * Copyright (C) 2009, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2011 Apple 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.
@@ skipping 522 matching lines @@
     }
 }
 
 bool FrameLoaderClientImpl::navigateBackForward(int offset) const
 {
     WebViewImpl* webview = m_webFrame->viewImpl();
     if (!webview->client())
         return false;
 
     ASSERT(offset);
-    offset = std::min(offset, webview->client()->historyForwardListCount());
-    offset = std::max(offset, -webview->client()->historyBackListCount());

[Nate Chapin, 2014/10/22 19:57:18]

This min/max bounding is unnecessary. For backspace navigation, where the only
offsets are -1 and 1, bounding renders the navigation invalid by setting the
offset to 0. For normal back/forward navigations, we have always declared the
navigation invalid if the offset was out of bounds (in NavigationScheduler).

-    if (!offset)
+    if (offset > webview->client()->historyForwardListCount())
+        return false;
+    if (offset < -webview->client()->historyBackListCount())
         return false;
     webview->client()->navigateBackForwardSoon(offset);
     return true;
 }
 
 void FrameLoaderClientImpl::didAccessInitialDocument()
 {
     if (m_webFrame->client())
         m_webFrame->client()->didAccessInitialDocument(m_webFrame);
 }
@@ skipping 296 matching lines @@
     if (m_webFrame->client())
         m_webFrame->client()->didAbortLoading(m_webFrame);
 }
 
 void FrameLoaderClientImpl::dispatchDidChangeManifest()
 {
     if (m_webFrame->client())
         m_webFrame->client()->didChangeManifest(m_webFrame);
 }
 
+unsigned FrameLoaderClientImpl::backForwardLength()
+{
+    WebViewImpl* webview = m_webFrame->viewImpl();
+    if (!webview || !webview->client())
+        return 0;
+    return webview->client()->historyBackListCount() + 1 + webview->client()->historyForwardListCount();
+}
+
 } // namespace blink