Introduce WebPassOwnPtr.

public/platform/WebPrivateOwnPtr.h

Index: public/platform/WebPrivateOwnPtr.h
diff --git a/public/platform/WebPrivateOwnPtr.h b/public/platform/WebPrivateOwnPtr.h
index 8b911264417d86b5adb91e9572b670006470facb..72252576bb99ecc9dd6b859f26896e3e84b794e8 100644
--- a/public/platform/WebPrivateOwnPtr.h
+++ b/public/platform/WebPrivateOwnPtr.h
@@ -36,6 +36,35 @@
 
 namespace blink {
 
+template <typename T>
+class WebPrivatePassOwnPtr {
+public:
+    WebPrivatePassOwnPtr() : m_ptr(nullptr) {}
+    WebPrivatePassOwnPtr(decltype(nullptr)) : m_ptr(nullptr) {}
+    template <typename U>
+    WebPrivatePassOwnPtr(const WebPrivatePassOwnPtr<U>& o)

[kinuko, 2015/07/16 05:58:57]

Do we need this?

[yhirano, 2015/07/16 06:37:48]

Yes, if we pass a WebPrivatePassOwnPtr<Derived> to a function that takes a
WebPrivatePassOwnPtr<Base>. I think it is likely to happen.

+    {
+        m_ptr = o.m_ptr;
+        o.m_ptr = nullptr;
+    }
+    ~WebPrivatePassOwnPtr() { BLINK_ASSERT(!m_ptr); }
+    WebPrivatePassOwnPtr& operator =(const WebPrivatePassOwnPtr&) = delete;
+
+    T* get() const { return m_ptr; }

[kinuko, 2015/07/16 05:58:57]

Do we need this? I feel release() (in the other patch) and the assertion in the
dtor are all we need in our use case?

[yhirano, 2015/07/16 06:37:48]

Done.

+
+    template <typename U> friend class WebPrivateOwnPtr;
+    template <typename U> friend class WebPrivatePassOwnPtr;
+    template <typename U> friend WebPrivatePassOwnPtr<U> adoptWebPtr(U*);
+
+private:
+    explicit WebPrivatePassOwnPtr(T* ptr) : m_ptr(ptr) {}
+
+    mutable T* m_ptr;
+};
+
+template <typename T>
+WebPrivatePassOwnPtr<T> adoptWebPtr(T* p) { return WebPrivatePassOwnPtr<T>(p); }
+
 // This class is an implementation detail of the WebKit API.  It exists
 // to help simplify the implementation of WebKit interfaces that merely
 // wrap a pointer to a WebCore class. It's similar to WebPrivatePtr, but it
@@ -47,12 +76,15 @@ class WebPrivateOwnPtr : public WebNonCopyable {
 public:
     WebPrivateOwnPtr() : m_ptr(nullptr) {}
     WebPrivateOwnPtr(decltype(nullptr)) : m_ptr(nullptr) {}
-    ~WebPrivateOwnPtr() { BLINK_ASSERT(!m_ptr); }
-
-    explicit WebPrivateOwnPtr(T* ptr)
-        : m_ptr(ptr)
+    template <typename U>
+    WebPrivateOwnPtr(const WebPrivatePassOwnPtr<U>& o)

[kinuko, 2015/07/16 05:58:57]

Do we actually use this?

[yhirano, 2015/07/16 06:37:48]

Deleted.

     {
+        m_ptr = o.m_ptr;
+        o.m_ptr = nullptr;
     }
+    ~WebPrivateOwnPtr() { BLINK_ASSERT(!m_ptr); }
+
+    explicit WebPrivateOwnPtr(T* ptr) : m_ptr(ptr) {}
 
     T* get() const { return m_ptr; }