Remove support for Object.observe

src/ic/mips64/ic-mips64.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.
 
 #if V8_TARGET_ARCH_MIPS64
 
 #include "src/codegen.h"
 #include "src/ic/ic.h"
 #include "src/ic/ic-compiler.h"
 #include "src/ic/stub-cache.h"
@@ skipping 604 matching lines @@
   Register elements_map = a6;
   Register elements = a7;  // Elements array of the receiver.
   // a4 and a5 are used as general scratch registers.
 
   // Check that the key is a smi.
   __ JumpIfNotSmi(key, &maybe_name_key);
   // Check that the object isn't a smi.
   __ JumpIfSmi(receiver, &slow);
   // Get the map of the object.
   __ ld(receiver_map, FieldMemOperand(receiver, HeapObject::kMapOffset));
-  // Check that the receiver does not require access checks and is not observed.
-  // The generic stub does not perform map checks or handle observed objects.
+  // Check that the receiver does not require access checks.
+  // The generic stub does not perform map checks.
   __ lbu(a4, FieldMemOperand(receiver_map, Map::kBitFieldOffset));
-  __ And(a4, a4,
-         Operand(1 << Map::kIsAccessCheckNeeded | 1 << Map::kIsObserved));
+  __ And(a4, a4, Operand(1 << Map::kIsAccessCheckNeeded));
   __ Branch(&slow, ne, a4, Operand(zero_reg));
   // Check if the object is a JS array or not.
   __ lbu(a4, FieldMemOperand(receiver_map, Map::kInstanceTypeOffset));
   __ Branch(&array, eq, a4, Operand(JS_ARRAY_TYPE));
   // Check that the object is some kind of JSObject.
   __ Branch(&slow, lt, a4, Operand(FIRST_JS_OBJECT_TYPE));
 
   // Object case: Check key against length in the elements array.
   __ ld(elements, FieldMemOperand(receiver, JSObject::kElementsOffset));
   // Check array bounds. Both the key and the length of FixedArray are smis.
@@ skipping 264 matching lines @@
       break;
     default:
       UNIMPLEMENTED();
   }
   patcher.ChangeBranchCondition(branch_instr, opcode);
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS64