VM: Reland Inline instance object hash code into object header on 64bit.

runtime/vm/assembler_x64.h

Index: runtime/vm/assembler_x64.h
diff --git a/runtime/vm/assembler_x64.h b/runtime/vm/assembler_x64.h
index 0c17551a8659516fe0c99ae2f9f18306fe7a904a..ad19e6dc6991a97b5120426a658c058419396e27 100644
--- a/runtime/vm/assembler_x64.h
+++ b/runtime/vm/assembler_x64.h
@@ -690,16 +690,8 @@ class Assembler : public ValueObject {
 
   void lock();
   void cmpxchgl(const Address& address, Register reg);
-  void lock_cmpxchgl(const Address& address, Register reg) {
-    lock();
-    cmpxchgl(address, reg);
-  }
 
   void cmpxchgq(const Address& address, Register reg);
-  void lock_cmpxchgq(const Address& address, Register reg) {
-    lock();
-    cmpxchgq(address, reg);
-  }
 
   void cpuid();
 
@@ -801,6 +793,11 @@ class Assembler : public ValueObject {
     cmpxchgq(address, reg);
   }
 
+  void LockCmpxchgl(const Address& address, Register reg) {
+    lock();
+    cmpxchgl(address, reg);
+  }
+
   void PushRegisters(intptr_t cpu_register_set, intptr_t xmm_register_set);
   void PopRegisters(intptr_t cpu_register_set, intptr_t xmm_register_set);