Generate StyleRareNonInheritedData in ComputedStyleBase.

third_party/WebKit/Source/core/style/DataPersistent.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef DataPersistent_h
 #define DataPersistent_h
 
 #include <memory>
 #include "platform/heap/Handle.h"
 #include "platform/wtf/Allocator.h"
@@ skipping 24 matching lines @@
     if (other.data_)
       data_ = WTF::WrapUnique(new Persistent<T>(other.data_->Get()));
 
     // Invalidated, subsequent mutations will happen on a new copy.
     //
     // (Clearing |m_ownCopy| will not be observable over T, hence
     // the const_cast<> is considered acceptable here.)
     const_cast<DataPersistent&>(other).own_copy_ = false;
   }
 
+  DataPersistent(DataPersistent&& other)
+      : data_(std::move(other.data_)), own_copy_(other.own_copy_) {
+    other.own_copy_ = false;
+  }
+
   const T* Get() const { return data_ ? data_->Get() : nullptr; }
 
   const T& operator*() const { return data_ ? *Get() : nullptr; }
   const T* operator->() const { return Get(); }
 
   T* Access() {
     if (data_ && !own_copy_) {
       *data_ = (*data_)->Copy();
       own_copy_ = true;
     }
@@ skipping 12 matching lines @@
     return data_->Get() == o.data_->Get() || *data_->Get() == *o.data_->Get();
   }
 
   bool operator!=(const DataPersistent<T>& o) const {
     DCHECK(data_);
     DCHECK(o.data_);
     return data_->Get() != o.data_->Get() && *data_->Get() != *o.data_->Get();
   }
 
   void operator=(std::nullptr_t) { data_.clear(); }
+  DataPersistent& operator=(DataPersistent&& other) {
+    data_ = std::move(other.data_);
+    own_copy_ = other.own_copy_;
+    other.own_copy_ = false;

[alancutter (OOO until 2018), 2017/06/13 03:49:29]

Here's one way to avoid repetition of logic:

~DataPersistant();
new(this) DataPersistant(std::move(other));

Not sure if it's actually a good idea though, up to you if you want to use it.

[shend, 2017/06/13 20:54:43]

Lol I have no idea what that does :P, so I'll keep the current code.

+    return *this;
+  }
 
  private:
   // Reduce size of DataPersistent<> by delaying creation of Persistent<>.
   std::unique_ptr<Persistent<T>> data_;
   unsigned own_copy_ : 1;
 };
 
 }  // namespace blink
 
 #endif  // DataPersistent_h