Revert of Internalize strings in-place

src/code-stub-assembler.h

Index: src/code-stub-assembler.h
diff --git a/src/code-stub-assembler.h b/src/code-stub-assembler.h
index 2bfdbb459f2f87c0f1cae9ada0f781d1e6e6b58e..de9d73cfe7ed8f0af179b0504e64c24e41d8bc1f 100644
--- a/src/code-stub-assembler.h
+++ b/src/code-stub-assembler.h
@@ -741,6 +741,9 @@ class V8_EXPORT_PRIVATE CodeStubAssembler : public compiler::CodeAssembler {
   // Convert any object to a Primitive.
   Node* JSReceiverToPrimitive(Node* context, Node* input);
 
+  // Convert a String to a flat String.
+  Node* FlattenString(Node* string);
+
   enum ToIntegerTruncationMode {
     kNoTruncation,
     kTruncateMinusZero,
@@ -853,8 +856,7 @@ class V8_EXPORT_PRIVATE CodeStubAssembler : public compiler::CodeAssembler {
 
   // Various building blocks for stubs doing property lookups.
   void TryToName(Node* key, Label* if_keyisindex, Variable* var_index,
-                 Label* if_keyisunique, Variable* var_unique,
-                 Label* if_bailout);
+                 Label* if_keyisunique, Label* if_bailout);
 
   // Calculates array index for given dictionary entry and entry field.
   // See Dictionary::EntryToIndex().