[heap] Cleanup string factory methods a bit.

src/factory.h

Index: src/factory.h
diff --git a/src/factory.h b/src/factory.h
index 69ae7d9c16eaeb06450ff10214e9ba3e993a9d0c..b7602e023b061690f9b5b7fb26a62c74fa96b026 100644
--- a/src/factory.h
+++ b/src/factory.h
@@ -156,24 +156,21 @@ class Factory final {
 
   // Allocates an internalized string in old space based on the character
   // stream.
-  MUST_USE_RESULT Handle<String> NewInternalizedStringFromUtf8(
-      Vector<const char> str,
-      int chars,
-      uint32_t hash_field);
+  Handle<String> NewInternalizedStringFromUtf8(Vector<const char> str,
+                                               int chars, uint32_t hash_field);
 
-  MUST_USE_RESULT Handle<String> NewOneByteInternalizedString(
-      Vector<const uint8_t> str, uint32_t hash_field);
+  Handle<String> NewOneByteInternalizedString(Vector<const uint8_t> str,
+                                              uint32_t hash_field);
 
-  MUST_USE_RESULT Handle<String> NewOneByteInternalizedSubString(
+  Handle<String> NewOneByteInternalizedSubString(
       Handle<SeqOneByteString> string, int offset, int length,
       uint32_t hash_field);
 
-  MUST_USE_RESULT Handle<String> NewTwoByteInternalizedString(
-        Vector<const uc16> str,
-        uint32_t hash_field);
+  Handle<String> NewTwoByteInternalizedString(Vector<const uc16> str,
+                                              uint32_t hash_field);
 
-  MUST_USE_RESULT Handle<String> NewInternalizedStringImpl(
-      Handle<String> string, int chars, uint32_t hash_field);
+  Handle<String> NewInternalizedStringImpl(Handle<String> string, int chars,
+                                           uint32_t hash_field);
 
   // Compute the matching internalized string map for a string if possible.
   // Empty handle is returned if string is in new space or not flattened.
@@ -197,14 +194,6 @@ class Factory final {
   // Create a new cons string object which consists of a pair of strings.
   MUST_USE_RESULT MaybeHandle<String> NewConsString(Handle<String> left,
                                                     Handle<String> right);
-  MUST_USE_RESULT MaybeHandle<String> NewOneByteConsString(
-      int length, Handle<String> left, Handle<String> right);
-  MUST_USE_RESULT MaybeHandle<String> NewTwoByteConsString(
-      int length, Handle<String> left, Handle<String> right);
-  MUST_USE_RESULT MaybeHandle<String> NewRawConsString(Handle<Map> map,
-                                                       int length,
-                                                       Handle<String> left,
-                                                       Handle<String> right);
 
   // Create a new string object which holds a proper substring of a string.
   Handle<String> NewProperSubString(Handle<String> str,