Adds the IsNull() matcher.

include/gmock/gmock-matchers.h

@@ -621,6 +621,19 @@ GMOCK_IMPLEMENT_COMPARISON_MATCHER_(Ne, !=, "not equal to");
 
 #undef GMOCK_IMPLEMENT_COMPARISON_MATCHER_
 
+// Implements the polymorphic IsNull() matcher, which matches any
+// pointer that is NULL.
+class IsNullMatcher {
+ public:
+  template <typename T>
+  bool Matches(T* p) const { return p == NULL; }
+
+  void DescribeTo(::std::ostream* os) const { *os << "is NULL"; }
+  void DescribeNegationTo(::std::ostream* os) const {
+    *os << "is not NULL";
+  }
+};
+
 // Implements the polymorphic NotNull() matcher, which matches any
 // pointer that is not NULL.
 class NotNullMatcher {
@@ -2319,6 +2332,11 @@ inline internal::NeMatcher<Rhs> Ne(Rhs x) {
   return internal::NeMatcher<Rhs>(x);
 }
 
+// Creates a polymorphic matcher that matches any NULL pointer.
+inline PolymorphicMatcher<internal::IsNullMatcher > IsNull() {
+  return MakePolymorphicMatcher(internal::IsNullMatcher());
+}
+
 // Creates a polymorphic matcher that matches any non-NULL pointer.
 // This is convenient as Not(NULL) doesn't compile (the compiler
 // thinks that that expression is comparing a pointer with an integer).