Fix HashTraits<blink::PropertyHandle>

HashTraits<blink::PropertyHandle>'s IsDeketedValue method was declared
as accepting blink::PropertyHandle. The argument should have been
const blink::PropertyHandle& (as it is in the parent class).
As a result, when trying to use this method, PropertyHandle was copied
resulting in a crash when traced by concurrent markers.

Bug: 986235
Change-Id: I0f29d37453f5c948bfd6e041e2979c9dbe144366
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1764157Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#689455}

third_party/blink/renderer/core/animation/property_handle.h

@@ -100,7 +100,7 @@ class CORE_EXPORT PropertyHandle {
     return PropertyHandle(kHandleDeletedValueForHashTraits);
   }
 
-  bool IsDeletedValueForHashTraits() {
+  bool IsDeletedValueForHashTraits() const {
     return handle_type_ == kHandleDeletedValueForHashTraits;
   }
 
@@ -143,7 +143,7 @@ struct HashTraits<blink::PropertyHandle>
     new (NotNull, &slot) blink::PropertyHandle(
         blink::PropertyHandle::DeletedValueForHashTraits());
   }
-  static bool IsDeletedValue(blink::PropertyHandle value) {
+  static bool IsDeletedValue(const blink::PropertyHandle& value) {
     return value.IsDeletedValueForHashTraits();
   }