Add an unimplemented history API to WebView

public/web/WebHistoryCommitType.h

Index: public/web/WebHistoryCommitType.h
diff --git a/public/web/WebHistoryCommitType.h b/public/web/WebHistoryCommitType.h
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+// Copyright 2014 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 WebHistoryCommitType_h
+#define WebHistoryCommitType_h
+
+namespace blink {
+
+enum WebHistoryCommitType {
+    // The default case (link clicks, user-typed urls, etc.), appends
+    // a new history entry to the back/forward list.
+    WebStandardCommit,
+    // A load that originated from history, whether from the
+    // back/forward list or session restore. The back/forward list is
+    // not modified, but our position in the list is.
+    WebBackForwardCommit,
+    // Each history entry is represented by a tree, where each node
+    // contains the history state of a single frame in the page. Initial
+    // loads in a new subframe append a new node to that tree.
+    WebInitialCommitInChildFrame,
+    // Reloads, client redirects, etc. Loads that neither originate from
+    // nor add entries to the back/forward list.
+    WebHistoryInertCommit
+};
+
+} // namespace blink
+
+#endif