[cleanup] Remove dead %StringCharFromCode runtime function.

Bug: v8:8015
Change-Id: Iaeaaa5a1ccded0b6e43bd78dd04cc0b8e2c933a3
Reviewed-on: https://chromium-review.googlesource.com/1238495Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56140}

src/compiler/typer.cc

@@ -1724,8 +1724,6 @@ Type Typer::Visitor::TypeJSCallRuntime(Node* node) {
       return Type::Boolean();
     case Runtime::kInlineCreateIterResultObject:
       return Type::OtherObject();
-    case Runtime::kInlineStringCharFromCode:
-      return Type::String();
     case Runtime::kInlineToLength:
       return TypeUnaryOp(node, ToLength);
     case Runtime::kInlineToNumber:

src/runtime/runtime-strings.cc

@@ -701,17 +701,6 @@ RUNTIME_FUNCTION(Runtime_FlattenString) {
   return *String::Flatten(isolate, str);
 }
 
-RUNTIME_FUNCTION(Runtime_StringCharFromCode) {
-  HandleScope handlescope(isolate);
-  DCHECK_EQ(1, args.length());
-  if (args[0]->IsNumber()) {
-    CONVERT_NUMBER_CHECKED(uint32_t, code, Uint32, args[0]);
-    code &= 0xFFFF;
-    return *isolate->factory()->LookupSingleCharacterStringFromCode(code);
-  }
-  return ReadOnlyRoots(isolate).empty_string();
-}
-
 RUNTIME_FUNCTION(Runtime_StringMaxLength) {
   SealHandleScope shs(isolate);
   return Smi::FromInt(String::kMaxLength);

src/runtime/runtime.h

@@ -411,7 +411,6 @@ namespace internal {
   F(StringBuilderConcat, 3, 1)            \
   F(StringBuilderJoin, 3, 1)              \
   F(StringCharCodeAt, 2, 1)               \
-  F(StringCharFromCode, 1, 1)             \
   F(StringEqual, 2, 1)                    \
   F(StringGreaterThan, 2, 1)              \
   F(StringGreaterThanOrEqual, 2, 1)       \