Move platform abstraction to base library

src/base/platform/semaphore.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_SEMAPHORE_H_
-#define V8_PLATFORM_SEMAPHORE_H_
+#ifndef V8_BASE_PLATFORM_SEMAPHORE_H_
+#define V8_BASE_PLATFORM_SEMAPHORE_H_
 
 #include "src/base/lazy-instance.h"
 #if V8_OS_WIN
 #include "src/base/win32-headers.h"
 #endif
 
 #if V8_OS_MACOSX
 #include <mach/semaphore.h>  // NOLINT
 #elif V8_OS_POSIX
 #include <semaphore.h>  // NOLINT
 #endif
 
 namespace v8 {
-namespace internal {
+namespace base {
 
 // Forward declarations.
 class TimeDelta;
 
 // ----------------------------------------------------------------------------
 // Semaphore
 //
 // A semaphore object is a synchronization object that maintains a count. The
 // count is decremented each time a thread completes a wait for the semaphore
 // object and incremented each time a thread signals the semaphore. When the
@@ skipping 52 matching lines @@
 
 template <int N>
 struct CreateSemaphoreTrait {
   static Semaphore* Create() {
     return new Semaphore(N);
   }
 };
 
 template <int N>
 struct LazySemaphore {
-  typedef typename v8::base::LazyDynamicInstance<
-      Semaphore,
-      CreateSemaphoreTrait<N>,
-      v8::base::ThreadSafeInitOnceTrait>::type type;
+  typedef typename LazyDynamicInstance<Semaphore, CreateSemaphoreTrait<N>,
+                                       ThreadSafeInitOnceTrait>::type type;
 };
 
 #define LAZY_SEMAPHORE_INITIALIZER LAZY_DYNAMIC_INSTANCE_INITIALIZER
 
-} }  // namespace v8::internal
+} }  // namespace v8::base
 
-#endif  // V8_PLATFORM_SEMAPHORE_H_
+#endif  // V8_BASE_PLATFORM_SEMAPHORE_H_