fix indentation and be more explicit re cast to gpr_atm

src/core/support/stack_lockfree.c

@@ -129,7 +129,7 @@ int gpr_stack_lockfree_push(gpr_stack_lockfree *stack, int entry) {
 
     old_val = gpr_atm_no_barrier_fetch_add(&stack->pushed[pushed_index],
                                            ((gpr_atm)1 << pushed_bit));
-	GPR_ASSERT((old_val & ((gpr_atm)1 << pushed_bit)) == 0);
+    GPR_ASSERT((old_val & (((gpr_atm)1) << pushed_bit)) == 0);
   }
 #endif
 
@@ -167,7 +167,7 @@ int gpr_stack_lockfree_pop(gpr_stack_lockfree *stack) {
 
     old_val = gpr_atm_no_barrier_fetch_add(&stack->pushed[pushed_index],
                                            -((gpr_atm)1 << pushed_bit));
-	GPR_ASSERT((old_val & ((gpr_atm)1 << pushed_bit)) != 0);
+    GPR_ASSERT((old_val & (((gpr_atm)1) << pushed_bit)) != 0);
   }
 #endif