Introduce HistoryClient interface

chrome/browser/history/chrome_history_client.cc

Index: chrome/browser/history/chrome_history_client.cc
diff --git a/tools/clang/blink_gc_plugin/tests/stack_allocated.cpp b/chrome/browser/history/chrome_history_client.cc
similarity index 62%
copy from tools/clang/blink_gc_plugin/tests/stack_allocated.cpp
copy to chrome/browser/history/chrome_history_client.cc
index e8a513435f7fdb5194dbaba7438288da6f0fbb0a..d6310c8877dba3a05ee40586620174f39d1d26c8 100644
--- a/tools/clang/blink_gc_plugin/tests/stack_allocated.cpp
+++ b/chrome/browser/history/chrome_history_client.cc
@@ -2,12 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "stack_allocated.h"
-
-namespace WebCore {
-
-void HeapObject::trace(Visitor* visitor)
-{
-}
+#include "chrome/browser/history/chrome_history_client.h"
 
+ChromeHistoryClient::ChromeHistoryClient() {
 }