Remove BackForwardClient, cleanup starting a history navigation

Source/web/FrameLoaderClientImpl.cpp

Index: Source/web/FrameLoaderClientImpl.cpp
diff --git a/Source/web/FrameLoaderClientImpl.cpp b/Source/web/FrameLoaderClientImpl.cpp
index f76882975b9aa0a6081406973539e328c9e50581..6c140aa0bd0ff00c4c91ee7bdf67d1302037428f 100644
--- a/Source/web/FrameLoaderClientImpl.cpp
+++ b/Source/web/FrameLoaderClientImpl.cpp
@@ -540,9 +540,9 @@ bool FrameLoaderClientImpl::navigateBackForward(int offset) const
         return false;
 
     ASSERT(offset);
-    offset = std::min(offset, webview->client()->historyForwardListCount());
-    offset = std::max(offset, -webview->client()->historyBackListCount());
-    if (!offset)
+    if (offset > webview->client()->historyForwardListCount())
+        return false;
+    if (offset < -webview->client()->historyBackListCount())
         return false;
     webview->client()->navigateBackForwardSoon(offset);
     return true;
@@ -866,4 +866,12 @@ void FrameLoaderClientImpl::dispatchDidChangeManifest()
         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