Remove support for Object.observe

src/code-stubs-hydrogen.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/code-stubs.h"
 
 #include "src/bailout-reason.h"
 #include "src/crankshaft/hydrogen.h"
 #include "src/crankshaft/lithium.h"
 #include "src/field-index.h"
@@ skipping 745 matching lines @@
         Add<HConstant>(static_cast<int>(Map::IsPrototypeMapBits::kMask) |
                        (1 << Map::kIsExtensible));
     HValue* bits = AddUncasted<HBitwise>(Token::BIT_AND, bit_field2, mask);
     IfBuilder check(this);
     check.If<HCompareNumericAndBranch>(
         bits, Add<HConstant>(1 << Map::kIsExtensible), Token::NE);
     check.ThenDeopt(Deoptimizer::kFastArrayPushFailed);
     check.End();
   }
 
-  // Disallow pushing onto observed objects.
-  {
-    HValue* bit_field =
-        Add<HLoadNamedField>(map, nullptr, HObjectAccess::ForMapBitField());
-    HValue* mask = Add<HConstant>(1 << Map::kIsObserved);
-    HValue* bit = AddUncasted<HBitwise>(Token::BIT_AND, bit_field, mask);
-    IfBuilder check(this);
-    check.If<HCompareNumericAndBranch>(bit, mask, Token::EQ);
-    check.ThenDeopt(Deoptimizer::kFastArrayPushFailed);
-    check.End();
-  }
-
   // Disallow pushing onto arrays in dictionary named property mode. We need to
   // figure out whether the length property is still writable.
   {
     HValue* bit_field3 =
         Add<HLoadNamedField>(map, nullptr, HObjectAccess::ForMapBitField3());
     HValue* mask = Add<HConstant>(static_cast<int>(Map::DictionaryMap::kMask));
     HValue* bit = AddUncasted<HBitwise>(Token::BIT_AND, bit_field3, mask);
     IfBuilder check(this);
     check.If<HCompareNumericAndBranch>(bit, mask, Token::EQ);
     check.ThenDeopt(Deoptimizer::kFastArrayPushFailed);
@@ skipping 1516 matching lines @@
   return Pop();
 }
 
 
 Handle<Code> KeyedLoadGenericStub::GenerateCode() {
   return DoGenerateCode(this);
 }
 
 }  // namespace internal
 }  // namespace v8