Revert of Implement WTF::WeakPtr in terms of base::WeakPtr

third_party/WebKit/Source/wtf/Forward.h

Index: third_party/WebKit/Source/wtf/Forward.h
diff --git a/third_party/WebKit/Source/wtf/Forward.h b/third_party/WebKit/Source/wtf/Forward.h
index 66e891c4bd1f590b032f57ace6386962b8832a27..521fffe8311dd7c3be4305d4ae064d2cff86e2cc 100644
--- a/third_party/WebKit/Source/wtf/Forward.h
+++ b/third_party/WebKit/Source/wtf/Forward.h
@@ -31,6 +31,7 @@
 template <size_t size> class SizeSpecificPartitionAllocator;
 template <typename T> class StringBuffer;
 template <typename T, size_t inlineCapacity, typename Allocator> class Vector;
+template <typename T> class WeakPtr;
 
 class ArrayBuffer;
 class ArrayBufferView;
@@ -56,6 +57,7 @@
 using WTF::PassRefPtr;
 using WTF::RefPtr;
 using WTF::Vector;
+using WTF::WeakPtr;
 
 using WTF::ArrayBuffer;
 using WTF::ArrayBufferView;