Remove support for Object.observe

src/ic/mips/ic-mips.cc

Index: src/ic/mips/ic-mips.cc
diff --git a/src/ic/mips/ic-mips.cc b/src/ic/mips/ic-mips.cc
index 46de1fd36f9b112df7c744f0383e92306509b09d..6c44918e103cc21fbae270e0ed0780efd9e63cf4 100644
--- a/src/ic/mips/ic-mips.cc
+++ b/src/ic/mips/ic-mips.cc
@@ -616,11 +616,10 @@ void KeyedStoreIC::GenerateMegamorphic(MacroAssembler* masm,
   __ 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));