Made PassRefPtr move only and replaced new copies with moves.

third_party/WebKit/Source/wtf/PassRefPtr.h

Index: third_party/WebKit/Source/wtf/PassRefPtr.h
diff --git a/third_party/WebKit/Source/wtf/PassRefPtr.h b/third_party/WebKit/Source/wtf/PassRefPtr.h
index 5bf92abc3633dc551e4138382fa6c1296122856e..af7a292005b33eb50b372ebc327156d5221e3ee6 100644
--- a/third_party/WebKit/Source/wtf/PassRefPtr.h
+++ b/third_party/WebKit/Source/wtf/PassRefPtr.h
@@ -71,11 +71,6 @@ class PassRefPtr {
   PassRefPtr() : m_ptr(nullptr) {}
   PassRefPtr(std::nullptr_t) : m_ptr(nullptr) {}
   PassRefPtr(T* ptr) : m_ptr(ptr) { refIfNotNull(ptr); }
-  // It somewhat breaks the type system to allow transfer of ownership out of
-  // a const PassRefPtr. However, it makes it much easier to work with
-  // PassRefPtr temporaries, and we don't have a need to use real const
-  // PassRefPtrs anyway.
-  PassRefPtr(const PassRefPtr& o) : m_ptr(o.leakRef()) {}
   PassRefPtr(PassRefPtr&& o) : m_ptr(o.leakRef()) {}
   template <typename U>
   PassRefPtr(const PassRefPtr<U>& o, EnsurePtrConvertibleArgDecl(U, T))