[esnext] implement frontend changes for async/await proposal

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 2ae54dd4a266972e67972249e059624d7472396d..903512b0312e7a152a00060848407f2f16451052 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -4295,7 +4295,7 @@ class ScopeInfo : public FixedArray {
   class HasSimpleParametersField
       : public BitField<bool, AsmFunctionField::kNext, 1> {};
   class FunctionKindField
-      : public BitField<FunctionKind, HasSimpleParametersField::kNext, 8> {};
+      : public BitField<FunctionKind, HasSimpleParametersField::kNext, 9> {};
 
   // BitFields representing the encoded information for context locals in the
   // ContextLocalInfoEntries part.
@@ -6853,6 +6853,13 @@ class SharedFunctionInfo: public HeapObject {
   // Indicates that this function is a generator.
   DECL_BOOLEAN_ACCESSORS(is_generator)
 
+  // Indicates that this function is an async function.
+  DECL_BOOLEAN_ACCESSORS(is_async)
+
+  // Indicates that this function can be suspended, either via YieldExpressions
+  // or AwaitExpressions.
+  inline bool is_resumable() const;
+
   // Indicates that this function is an arrow function.
   DECL_BOOLEAN_ACCESSORS(is_arrow)
 
@@ -7149,6 +7156,7 @@ class SharedFunctionInfo: public HeapObject {
     kIsGetterFunction,
     kIsSetterFunction,
     // byte 3
+    kIsAsyncFunction,
     kDeserialized,
     kIsDeclaration,
     kCompilerHintsCount,  // Pseudo entry
@@ -7171,7 +7179,7 @@ class SharedFunctionInfo: public HeapObject {
   ASSERT_FUNCTION_KIND_ORDER(kSetterFunction, kIsSetterFunction);
 #undef ASSERT_FUNCTION_KIND_ORDER
 
-  class FunctionKindBits : public BitField<FunctionKind, kIsArrow, 8> {};
+  class FunctionKindBits : public BitField<FunctionKind, kIsArrow, 9> {};
 
   class DeoptCountBits : public BitField<int, 0, 4> {};
   class OptReenableTriesBits : public BitField<int, 4, 18> {};