[esnext] implement frontend changes for async/await proposal

src/globals.h

Index: src/globals.h
diff --git a/src/globals.h b/src/globals.h
index 7167423a48e125f96cf6254af65b467994f597f2..827857d4d0faeb2e49a6ce716a1c6f4a162e6229 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -944,11 +944,14 @@ enum FunctionKind {
   kBaseConstructor = 1 << 5,
   kGetterFunction = 1 << 6,
   kSetterFunction = 1 << 7,
+  kAsyncFunction = 1 << 8,
   kAccessorFunction = kGetterFunction | kSetterFunction,
   kDefaultBaseConstructor = kDefaultConstructor | kBaseConstructor,
   kDefaultSubclassConstructor = kDefaultConstructor | kSubclassConstructor,
   kClassConstructor =
       kBaseConstructor | kSubclassConstructor | kDefaultConstructor,
+  kAsyncArrowFunction = kArrowFunction | kAsyncFunction,
+  kAsyncConciseMethod = kAsyncFunction | kConciseMethod
 };
 
 inline bool IsValidFunctionKind(FunctionKind kind) {
@@ -963,7 +966,10 @@ inline bool IsValidFunctionKind(FunctionKind kind) {
          kind == FunctionKind::kDefaultBaseConstructor ||
          kind == FunctionKind::kDefaultSubclassConstructor ||
          kind == FunctionKind::kBaseConstructor ||
-         kind == FunctionKind::kSubclassConstructor;
+         kind == FunctionKind::kSubclassConstructor ||
+         kind == FunctionKind::kAsyncFunction ||
+         kind == FunctionKind::kAsyncArrowFunction ||
+         kind == FunctionKind::kAsyncConciseMethod;
 }
 
 
@@ -978,6 +984,10 @@ inline bool IsGeneratorFunction(FunctionKind kind) {
   return kind & FunctionKind::kGeneratorFunction;
 }
 
+inline bool IsAsyncFunction(FunctionKind kind) {
+  DCHECK(IsValidFunctionKind(kind));
+  return kind & FunctionKind::kAsyncFunction;
+}
 
 inline bool IsConciseMethod(FunctionKind kind) {
   DCHECK(IsValidFunctionKind(kind));