Run clang-tidy modernize-use-equals-{delete,default} on //base headers

This CL only touches base headers (the headers were accidentally
excluded from the previous change to cc files).

This change was done using clang-tidy as described here:
https://chromium.googlesource.com/chromium/src/+/lkcr/docs/clang_tidy.md

BUG=778959,778957

Change-Id: I4d3b4ca1218b835a671c2e0c8f31c2b528e25a0c
Reviewed-on: https://chromium-review.googlesource.com/813316
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Chris Watkins <watk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#523687}

CrOS-Libchrome-Original-Commit: 091d6297a7ba73390b37f856cc8c61813403a047
diff --git a/base/bind_internal.h b/base/bind_internal.h
index 9af3ed2..9d5720f 100644
--- a/base/bind_internal.h
+++ b/base/bind_internal.h
@@ -484,7 +484,7 @@
     DCHECK(!IsNull(functor_));
   }
 
-  ~BindState() {}
+  ~BindState() = default;
 
   static void Destroy(const BindStateBase* self) {
     delete static_cast<const BindState*>(self);