Purge UnspecifiedBoolType from Blink.

third_party/WebKit/Source/bindings/core/v8/Nullable.h

Index: third_party/WebKit/Source/bindings/core/v8/Nullable.h
diff --git a/third_party/WebKit/Source/bindings/core/v8/Nullable.h b/third_party/WebKit/Source/bindings/core/v8/Nullable.h
index 8598486bc264ce6e7ded39d8147e431fbebef3b3..31b0f612b59794229104dbd2f5f2aa2c7e75ddd9 100644
--- a/third_party/WebKit/Source/bindings/core/v8/Nullable.h
+++ b/third_party/WebKit/Source/bindings/core/v8/Nullable.h
@@ -65,9 +65,7 @@ public:
     T& get() { ASSERT(!m_isNull); return m_value; }
     bool isNull() const { return m_isNull; }
 
-    // See comment in RefPtr.h about what UnspecifiedBoolType is.
-    typedef const T* UnspecifiedBoolType;
-    operator UnspecifiedBoolType() const { return m_isNull ? 0 : &m_value; }
+    explicit operator bool() const { return !m_isNull; }
 
     bool operator==(const Nullable& other) const
     {