Generate StyleRareNonInheritedData in ComputedStyleBase.

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

Index: third_party/WebKit/Source/core/style/DataPersistent.h
diff --git a/third_party/WebKit/Source/core/style/DataPersistent.h b/third_party/WebKit/Source/core/style/DataPersistent.h
index 3672b6a7909f96fbd37a49502e3ef5634a75188b..e8451aba778846b33aa794e9915f0b87002015df 100644
--- a/third_party/WebKit/Source/core/style/DataPersistent.h
+++ b/third_party/WebKit/Source/core/style/DataPersistent.h
@@ -42,6 +42,11 @@ class DataPersistent {
     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; }
@@ -74,6 +79,12 @@ class DataPersistent {
   }
 
   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<>.