Reland "[turbofan] inline %StringIteratorPrototype%.next in JSBuiltinReducer"

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 d5dc9c963d8f4f3f8bb9d5baf051d6ed1ff2b7ae..c55f48cb9640b18a5bacd294109a94de82ed956c 100644
--- a/src/code-stub-assembler.h
+++ b/src/code-stub-assembler.h
@@ -19,12 +19,6 @@ class StubCache;
 
 enum class PrimitiveType { kBoolean, kNumber, kString, kSymbol };
 
-enum class UnicodeEncoding {
-  // Different unicode encodings in a |word32|:
-  UTF16,  // hi 16bits -> trailing surrogate or 0, low 16bits -> lead surrogate
-  UTF32,  // full UTF32 code unit / Unicode codepoint
-};
-
 #define HEAP_CONSTANT_LIST(V)                 \
   V(BooleanMap, BooleanMap)                   \
   V(empty_string, EmptyString)                \