[ESnext] Stage Promise.prototype.finally

Bug: v8:5967
Change-Id: I10388495158fe72ff06cc0f9f9a7b9522705f6e6
Reviewed-on: https://chromium-review.googlesource.com/658301Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47932}

src/flag-definitions.h

@@ -193,8 +193,7 @@ DEFINE_IMPLICATION(es_staging, harmony)
   V(harmony_array_prototype_values, "harmony Array.prototype.values") \
   V(harmony_function_sent, "harmony function.sent")                   \
   V(harmony_do_expressions, "harmony do-expressions")                 \
-  V(harmony_class_fields, "harmony public fields in class literals")  \
-  V(harmony_promise_finally, "harmony Promise.prototype.finally")
+  V(harmony_class_fields, "harmony public fields in class literals")
 
 #ifdef V8_INTL_SUPPORT
 #define HARMONY_INPROGRESS(V)                    \
@@ -216,6 +215,7 @@ DEFINE_IMPLICATION(es_staging, harmony)
     "constructor")                                                      \
   V(harmony_dynamic_import, "harmony dynamic import")                   \
   V(harmony_async_iteration, "harmony async iteration")                 \
+  V(harmony_promise_finally, "harmony Promise.prototype.finally")
 
 // Features that are shipping (turned on by default, but internal flag remains).
 #define HARMONY_SHIPPING(V)                                              \