Use the SEQUENCE_CHECKER macro in WeakPtr instead of manual #ifdefs

Bug: NONE
Change-Id: I4267bed9b5e2d47822dfe023c138417d3b60c643
Reviewed-on: https://chromium-review.googlesource.com/577399
Commit-Queue: Hans Wennborg <hans@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487916}

base/memory/weak_ptr.cc

@@ -9,19 +9,17 @@
 namespace base {
 namespace internal {
 
-static constexpr uintptr_t kTrueMask = ~static_cast<uintptr_t>(0);
+constexpr uintptr_t kTrueMask = ~static_cast<uintptr_t>(0);
 
 WeakReference::Flag::Flag() : is_valid_(kTrueMask) {
-#if DCHECK_IS_ON()
   // Flags only become bound when checked for validity, or invalidated,
   // so that we can check that later validity/invalidation operations on
   // the same Flag take place on the same sequenced thread.
-  sequence_checker_.DetachFromSequence();
-#endif
+  DETACH_FROM_SEQUENCE(sequence_checker_);
 }
 
 WeakReference::Flag::Flag(WeakReference::Flag::NullFlagTag) : is_valid_(false) {
-  // There is no need for sequence_checker_.DetachFromSequence() because the
+  // There is no need for DETACH_FROM_SEQUENCE(sequence_checker_) because the
   // null flag doesn't participate in the sequence checks. See DCHECK in
   // Invalidate() and IsValid().
 

base/memory/weak_ptr.h

@@ -114,8 +114,7 @@ class BASE_EXPORT WeakReference {
         DCHECK(!is_valid_);
         return 0;
       }
-      DCHECK(sequence_checker_.CalledOnValidSequence())
-          << "WeakPtrs must be checked on the same sequenced thread.";
+      DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
 #endif
       return is_valid_;
     }
@@ -129,11 +128,7 @@ class BASE_EXPORT WeakReference {
     ~Flag();
 
     uintptr_t is_valid_;
-#if DCHECK_IS_ON()
-    // Even if SequenceChecker is an empty class in non-dcheck builds, it still
-    // takes up space in the class.
-    SequenceChecker sequence_checker_;
-#endif
+    SEQUENCE_CHECKER(sequence_checker_);
   };
 
   WeakReference();