[es6] Stage --harmony-completion.

R=rossberg
BUG=

Review URL: https://codereview.chromium.org/1403683003

Cr-Commit-Position: refs/heads/master@{#31209}

src/flag-definitions.h

@@ -199,14 +199,14 @@ DEFINE_BOOL(legacy_const, true, "legacy semantics for const in sloppy mode")
   V(harmony_destructuring, "harmony destructuring")                   \
   V(harmony_default_parameters, "harmony default parameters")         \
   V(harmony_sharedarraybuffer, "harmony sharedarraybuffer")           \
-  V(harmony_simd, "harmony simd")                                     \
-  V(harmony_completion, "harmony completion value semantics")
+  V(harmony_simd, "harmony simd")
 
 // Features that are complete (but still behind --harmony/es-staging flag).
-#define HARMONY_STAGED(V)                                             \
-  V(harmony_tostring, "harmony toString")                             \
-  V(harmony_sloppy, "harmony features in sloppy mode")                \
-  V(harmony_sloppy_let, "harmony let in sloppy mode")
+#define HARMONY_STAGED(V)                              \
+  V(harmony_tostring, "harmony toString")              \
+  V(harmony_sloppy, "harmony features in sloppy mode") \
+  V(harmony_sloppy_let, "harmony let in sloppy mode")  \
+  V(harmony_completion, "harmony completion value semantics")
 
 // Features that are shipping (turned on by default, but internal flag remains).
 #define HARMONY_SHIPPING(V)                                     \

test/test262/test262.status

@@ -734,6 +734,11 @@
   'language/types/number/S8.5_A2.1': [PASS, FAIL_OK],
   'language/types/number/S8.5_A2.2': [PASS, FAIL_OK],
 
+  # 'if' should never return a completion whose value component is empty.
+  # https://bugs.ecmascript.org/show_bug.cgi?id=4540
+  'language/statements/for/S12.6.3_A9.1': [FAIL],
+  'language/statements/for/S12.6.3_A9': [FAIL],
+
   ############################ INVALID TESTS #############################
 
   # The reference value calculated by Test262 is incorrect if you run these