A64: Synchronize with r17807.

src/a64/ic-a64.cc

Index: src/a64/ic-a64.cc
diff --git a/src/a64/ic-a64.cc b/src/a64/ic-a64.cc
index e695f13473f7c51a7aa725006ed7a310ec0baf2b..a2fa028b80028699139e715fc96448372dbdb7df 100644
--- a/src/a64/ic-a64.cc
+++ b/src/a64/ic-a64.cc
@@ -1553,10 +1553,11 @@ void KeyedStoreIC::GenerateGeneric(MacroAssembler* masm,
   __ JumpIfSmi(receiver, &slow);
   __ Ldr(receiver_map, FieldMemOperand(receiver, HeapObject::kMapOffset));
 
-  // Check that the receiver does not require access checks. We need to do this
-  // because this generic stub does not perform map checks.
+  // 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.
   __ Ldrb(x10, FieldMemOperand(receiver_map, Map::kBitFieldOffset));
-  __ Tbnz(x10, Map::kIsAccessCheckNeeded, &slow);
+  __ TestAndBranchIfAnySet(
+      x10, (1 << Map::kIsAccessCheckNeeded) | (1 << Map::kIsObserved), &slow);
 
   // Check if the object is a JS array or not.
   Register instance_type = x10;