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 7ca6f715c50b3225480b9a6c951e788cf137a2c7..bc40b4d64508b2bc236284373b523a2cf0f77d70 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.insert(string).storedValue;