Remove support for Object.observe

src/ic/mips/ic-mips.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_MIPS
 
 #include "src/codegen.h"
 #include "src/ic/ic.h"
 #include "src/ic/ic-compiler.h"
 #include "src/ic/stub-cache.h"
@@ skipping 598 matching lines @@
   Register elements_map = t2;
   Register elements = t3;  // Elements array of the receiver.
   // t0 and t1 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.
   __ lw(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(t0, FieldMemOperand(receiver_map, Map::kBitFieldOffset));
-  __ And(t0, t0,
-         Operand(1 << Map::kIsAccessCheckNeeded | 1 << Map::kIsObserved));
+  __ And(t0, t0, Operand(1 << Map::kIsAccessCheckNeeded));
   __ Branch(&slow, ne, t0, Operand(zero_reg));
   // Check if the object is a JS array or not.
   __ lbu(t0, FieldMemOperand(receiver_map, Map::kInstanceTypeOffset));
   __ Branch(&array, eq, t0, Operand(JS_ARRAY_TYPE));
   // Check that the object is some kind of JS object EXCEPT JS Value type. In
   // the case that the object is a value-wrapper object, we enter the runtime
   // system to make sure that indexing into string objects works as intended.
   STATIC_ASSERT(JS_VALUE_TYPE < JS_OBJECT_TYPE);
   __ Branch(&slow, lo, t0, Operand(JS_OBJECT_TYPE));
 
@@ skipping 268 matching lines @@
       break;
     default:
       UNIMPLEMENTED();
   }
   patcher.ChangeBranchCondition(branch_instr, opcode);
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS