Refactor ChangeLowering class to avoid template specialization.

testing/gmock-support.h

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_TESTING_GMOCK_SUPPORT_H_
+#define V8_TESTING_GMOCK_SUPPORT_H_
+
+#include "testing/gmock/include/gmock/gmock.h"
+
+namespace testing {
+
+template <typename T>
+class Capture {
+ public:
+  Capture() : value_(), has_value_(false) {}
+
+  const T& value() const { return value_; }
+  bool has_value() const { return has_value_; }
+
+  void SetValue(const T& value) {
+    DCHECK(!has_value());
+    value_ = value;
+    has_value_ = true;
+  }
+
+ private:
+  T value_;
+  bool has_value_;
+};
+
+
+namespace internal {
+
+template <typename T>
+class CaptureEqMatcher : public MatcherInterface<T> {
+ public:
+  explicit CaptureEqMatcher(Capture<T>* capture) : capture_(capture) {}
+
+  virtual void DescribeTo(std::ostream* os) const {
+    *os << "captured by " << static_cast<const void*>(capture_);
+    if (capture_->has_value()) *os << " which has value " << capture_->value();
+  }
+
+  virtual bool MatchAndExplain(T value, MatchResultListener* listener) const {
+    if (!capture_->has_value()) {
+      capture_->SetValue(value);
+      return true;
+    }
+    if (value != capture_->value()) {
+      *listener << "which is not equal to " << capture_->value();
+      return false;
+    }
+    return true;
+  }
+
+ private:
+  Capture<T>* capture_;
+};
+
+}  // namespace internal
+
+
+// CaptureEq(capture) captures the value passed in during matching as long as it
+// is unset, and once set, compares the value for equality with the argument.
+template <typename T>
+Matcher<T> CaptureEq(Capture<T>* capture) {
+  return MakeMatcher(new internal::CaptureEqMatcher<T>(capture));
+}
+
+}  // namespace testing
+
+#endif  // V8_TESTING_GMOCK_SUPPORT_H_