Move platform abstraction to base library

src/base/platform/elapsed-timer.h

 // Copyright 2013 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_PLATFORM_ELAPSED_TIMER_H_
-#define V8_PLATFORM_ELAPSED_TIMER_H_
+#ifndef V8_BASE_PLATFORM_ELAPSED_TIMER_H_
+#define V8_BASE_PLATFORM_ELAPSED_TIMER_H_
 
-#include "src/checks.h"
-#include "src/platform/time.h"
+#include "src/base/logging.h"
+#include "src/base/platform/time.h"
 
 namespace v8 {
-namespace internal {
+namespace base {
 
-class ElapsedTimer V8_FINAL BASE_EMBEDDED {
+class ElapsedTimer V8_FINAL {
  public:
 #ifdef DEBUG
   ElapsedTimer() : started_(false) {}
 #endif
 
   // Starts this timer. Once started a timer can be checked with
   // |Elapsed()| or |HasExpired()|, and may be restarted using |Restart()|.
   // This method must not be called on an already started timer.
   void Start() {
     ASSERT(!IsStarted());
@@ skipping 60 matching lines @@
     ASSERT(!now.IsNull());
     return now;
   }
 
   TimeTicks start_ticks_;
 #ifdef DEBUG
   bool started_;
 #endif
 };
 
-} }  // namespace v8::internal
+} }  // namespace v8::base
 
-#endif  // V8_PLATFORM_ELAPSED_TIMER_H_
+#endif  // V8_BASE_PLATFORM_ELAPSED_TIMER_H_