Replace StringImpl::empty{16Bit}() with a static member

third_party/WebKit/Source/wtf/text/AtomicStringTable.cpp

Index: third_party/WebKit/Source/wtf/text/AtomicStringTable.cpp
diff --git a/third_party/WebKit/Source/wtf/text/AtomicStringTable.cpp b/third_party/WebKit/Source/wtf/text/AtomicStringTable.cpp
index c5126ab222debbe2415b7c04a54bb976bb7cd403..04ce0aca6e771a83b7503d0e39c20b5718828145 100644
--- a/third_party/WebKit/Source/wtf/text/AtomicStringTable.cpp
+++ b/third_party/WebKit/Source/wtf/text/AtomicStringTable.cpp
@@ -148,7 +148,7 @@ PassRefPtr<StringImpl> AtomicStringTable::add(const UChar* s, unsigned length) {
     return nullptr;
 
   if (!length)
-    return StringImpl::empty();
+    return StringImpl::empty;
 
   UCharBuffer buffer = {s, length};
   return addToStringTable<UCharBuffer, UCharBufferTranslator>(buffer);
@@ -178,7 +178,7 @@ PassRefPtr<StringImpl> AtomicStringTable::add(const LChar* s, unsigned length) {
     return nullptr;
 
   if (!length)
-    return StringImpl::empty();
+    return StringImpl::empty;
 
   LCharBuffer buffer = {s, length};
   return addToStringTable<LCharBuffer, LCharBufferTranslator>(buffer);
@@ -186,7 +186,7 @@ PassRefPtr<StringImpl> AtomicStringTable::add(const LChar* s, unsigned length) {
 
 StringImpl* AtomicStringTable::add(StringImpl* string) {
   if (!string->length())
-    return StringImpl::empty();
+    return StringImpl::empty;
 
   StringImpl* result = *m_table.add(string).storedValue;