Removed mutable from PassRefPtr's raw pointer member.

third_party/WebKit/Source/platform/wtf/PassRefPtr.h

Index: third_party/WebKit/Source/platform/wtf/PassRefPtr.h
diff --git a/third_party/WebKit/Source/platform/wtf/PassRefPtr.h b/third_party/WebKit/Source/platform/wtf/PassRefPtr.h
index f36ee84df5d6d6b403810bc10ef24dffe745f744..cde758fcf71b1225005feabe32df76938afb3d41 100644
--- a/third_party/WebKit/Source/platform/wtf/PassRefPtr.h
+++ b/third_party/WebKit/Source/platform/wtf/PassRefPtr.h
@@ -86,7 +86,7 @@ class PassRefPtr {
 
   T* Get() const { return ptr_; }
 
-  WARN_UNUSED_RESULT T* LeakRef() const;
+  WARN_UNUSED_RESULT T* LeakRef();
 
   T& operator*() const { return *ptr_; }
   T* operator->() const { return ptr_; }
@@ -105,7 +105,7 @@ class PassRefPtr {
     return *this;
   }
 
-  mutable T* ptr_;
+  T* ptr_;
 };
 
 template <typename T>
@@ -129,7 +129,7 @@ inline PassRefPtr<T>::PassRefPtr(RefPtr<U>&& o,
     : ptr_(o.LeakRef()) {}
 
 template <typename T>
-inline T* PassRefPtr<T>::LeakRef() const {
+inline T* PassRefPtr<T>::LeakRef() {
   T* ptr = ptr_;
   ptr_ = nullptr;
   return ptr;