Revert of Ship arrow functions (patchset #1 id:1 of https://codereview.chromium.org/1187173004/)

Reason for revert:
[Sheriff] Breaks layout tests. Please submit a needsmanualrebaseline change on the blink side for the expectations if intended.

E.g.
http://build.chromium.org/p/client.v8.fyi/builders/V8-Blink%20Linux%2064/builds/545

Original issue's description:
> Ship arrow functions
>
> R=rossberg@chromium.org
> LOG=Y
> BUG=v8:2700
>
> Committed: https://crrev.com/541b6c39e0ecae1c070f51fae8e9e3dab18d278c
> Cr-Commit-Position: refs/heads/master@{#29119}

TBR=rossberg@chromium.org,wingo@igalia.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:2700

Review URL: https://codereview.chromium.org/1182053013

Cr-Commit-Position: refs/heads/master@{#29125}

src/flag-definitions.h

@@ -199,6 +199,7 @@ DEFINE_IMPLICATION(es_staging, harmony)
 // Features that are complete (but still behind --harmony/es-staging flag).
 #define HARMONY_STAGED(V)                                      \
   V(harmony_arrays, "harmony array methods")                   \
+  V(harmony_arrow_functions, "harmony arrow functions")        \
   V(harmony_rest_parameters, "harmony rest parameters")        \
   V(harmony_spreadcalls, "harmony spread-calls")               \
   V(harmony_object, "harmony Object methods")                  \
@@ -207,7 +208,6 @@ DEFINE_IMPLICATION(es_staging, harmony)
 
 // Features that are shipping (turned on by default, but internal flag remains).
 #define HARMONY_SHIPPING(V)                                                \
-  V(harmony_arrow_functions, "harmony arrow functions")                    \
   V(harmony_classes, "harmony classes (implies object literal extension)") \
   V(harmony_computed_property_names, "harmony computed property names")    \
   V(harmony_object_literals, "harmony object literal extensions")          \