Use explicit WebString conversions in LayoutTest related files

content/test/layouttest_support.cc

Index: content/test/layouttest_support.cc
diff --git a/content/test/layouttest_support.cc b/content/test/layouttest_support.cc
index 3f981ddc9c333d4f23803857c9ab4321b90d9e6f..117f9bd066ab3b8484fedb3ca73e727e92d9d6b3 100644
--- a/content/test/layouttest_support.cc
+++ b/content/test/layouttest_support.cc
@@ -541,8 +541,8 @@ void DisableAutoResizeMode(RenderView* render_view, const WebSize& new_size) {
 // Returns True if node1 < node2.
 bool HistoryEntryCompareLess(HistoryEntry::HistoryNode* node1,
                              HistoryEntry::HistoryNode* node2) {
-  base::string16 target1 = node1->item().target();
-  base::string16 target2 = node2->item().target();
+  base::string16 target1 = node1->item().target().utf16();
+  base::string16 target2 = node2->item().target().utf16();
   return base::CompareCaseInsensitiveASCII(target1, target2) < 0;
 }