Implement basic code generation for arrow functions

tools/generate-runtime-tests.py

Index: tools/generate-runtime-tests.py
diff --git a/tools/generate-runtime-tests.py b/tools/generate-runtime-tests.py
index b1c00a6280ed1a7b3773368c7dca38e111452b74..ba7a7cc22000760a5c5db5f66309be5123559db5 100755
--- a/tools/generate-runtime-tests.py
+++ b/tools/generate-runtime-tests.py
@@ -47,8 +47,8 @@ EXPAND_MACROS = [
 # that the parser doesn't bit-rot. Change the values as needed when you add,
 # remove or change runtime functions, but make sure we don't lose our ability
 # to parse them!
-EXPECTED_FUNCTION_COUNT = 417
-EXPECTED_FUZZABLE_COUNT = 332
+EXPECTED_FUNCTION_COUNT = 418
+EXPECTED_FUZZABLE_COUNT = 333
 EXPECTED_CCTEST_COUNT = 8
 EXPECTED_UNKNOWN_COUNT = 4
 EXPECTED_BUILTINS_COUNT = 809
@@ -256,6 +256,7 @@ CUSTOM_KNOWN_GOOD_INPUT = {
   "TypedArrayInitialize": [None, 6, "new ArrayBuffer(8)", None, 4, None],
   "TypedArrayInitializeFromArrayLike": [None, 6, None, None, None],
   "TypedArraySetFastCases": [None, None, "0", None],
+  "FunctionIsArrow": ["() => null", None],
 }