[d8] implement console for d8.

src/d8-console.h

Index: src/d8-console.h
diff --git a/src/d8-console.h b/src/d8-console.h
new file mode 100644
index 0000000000000000000000000000000000000000..293cb21180e5d08de6020a3a6e15b3b00fbf6708
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+++ b/src/d8-console.h
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+// Copyright 2017 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_D8_CONSOLE_H_
+#define V8_D8_CONSOLE_H_
+
+#include "src/base/platform/time.h"
+#include "src/debug/debug-interface.h"
+#include "src/debug/interface-types.h"
+
+namespace v8 {
+
+class D8Console : public debug::ConsoleDelegate {
+ public:
+  explicit D8Console(Isolate* isolate);
+
+ private:
+  void Log(const debug::ConsoleCallArguments& args) override;
+  void Error(const debug::ConsoleCallArguments& args) override;
+  void Warn(const debug::ConsoleCallArguments& args) override;
+  void Info(const debug::ConsoleCallArguments& args) override;
+  void Debug(const debug::ConsoleCallArguments& args) override;
+  void Time(const debug::ConsoleCallArguments& args) override;
+  void TimeEnd(const debug::ConsoleCallArguments& args) override;
+
+  Isolate* isolate_;
+  std::map<std::string, base::TimeTicks> timers_;
+  base::TimeTicks default_timer_;
+};
+
+}  // namespace v8
+
+#endif  // V8_D8_CONSOLE_H_