Revert "Enable Object.observe by default"

src/flag-definitions.h

Index: src/flag-definitions.h
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index a882d03b23a328d12e4b7130ab79c70e090fb6f8..8c3f39db041ae75701e9bc9ebae3ec6b1a978988 100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -179,6 +179,8 @@ DEFINE_bool(harmony_promises, false, "enable harmony promises")
 DEFINE_bool(harmony_proxies, false, "enable harmony proxies")
 DEFINE_bool(harmony_collections, false,
             "enable harmony collections (sets, maps, and weak maps)")
+DEFINE_bool(harmony_observation, false,
+            "enable harmony object observation (implies harmony collections")
 DEFINE_bool(harmony_generators, false, "enable harmony generators")
 DEFINE_bool(harmony_iteration, false, "enable harmony iteration (for-of)")
 DEFINE_bool(harmony_numeric_literals, false,
@@ -194,6 +196,7 @@ DEFINE_implication(harmony, harmony_symbols)
 DEFINE_implication(harmony, harmony_promises)
 DEFINE_implication(harmony, harmony_proxies)
 DEFINE_implication(harmony, harmony_collections)
+DEFINE_implication(harmony, harmony_observation)
 DEFINE_implication(harmony, harmony_generators)
 DEFINE_implication(harmony, harmony_iteration)
 DEFINE_implication(harmony, harmony_numeric_literals)
@@ -202,6 +205,7 @@ DEFINE_implication(harmony, harmony_arrays)
 DEFINE_implication(harmony, harmony_maths)
 DEFINE_implication(harmony_promises, harmony_collections)
 DEFINE_implication(harmony_modules, harmony_scoping)
+DEFINE_implication(harmony_observation, harmony_collections)
 
 // Flags for experimental implementation features.
 DEFINE_bool(packed_arrays, true, "optimizes arrays that have no holes")