Try flattening strings before comparing for equality.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index ad151041528b3a7e4b75146eda063f7f68e09549..d82d73ec50108cd6526799bc30601a8ccf364681 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -1691,13 +1691,19 @@ bool String::Equals(String* other) {
 
 
 Object* String::TryFlatten(PretenureFlag pretenure) {
-  // We don't need to flatten strings that are already flat.  Since this code
-  // is inlined, it can be helpful in the flat case to not call out to Flatten.
-  if (IsFlat()) return this;
+  if (!StringShape(this).IsCons()) return this;

[Mads Ager (chromium), 2010/05/19 12:27:43]

StringShapes should be deprecated, they were a failed optimization attempt.
Please just use IsConsString() here.

+  ConsString* cons = ConsString::cast(this);
+  if (cons->second()->length() == 0) return cons->first();
   return SlowTryFlatten(pretenure);
 }
 
 
+String* String::TryFlattenGetString(PretenureFlag pretenure) {
+  Object* flat = TryFlatten(pretenure);
+  return flat->IsFailure() ? this : String::cast(flat);
+}
+
+
 uint16_t String::Get(int index) {
   ASSERT(index >= 0 && index < length());
   switch (StringShape(this).full_representation_tag()) {