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 e1e8a4b3963b93795bc98d1cbe27b53fdc25dbce..36bef9063804dca755a5837bef17630b400938e7 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")