Move platform abstraction to base library

src/runtime-profiler.h

 // Copyright 2012 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_RUNTIME_PROFILER_H_
 #define V8_RUNTIME_PROFILER_H_
 
 #include "src/allocation.h"
 
 namespace v8 {
+
+namespace base {
+class Semaphore;
+}
+
 namespace internal {
 
 class Isolate;
 class JSFunction;
 class Object;
-class Semaphore;
 
 class RuntimeProfiler {
  public:
   explicit RuntimeProfiler(Isolate* isolate);
 
   void OptimizeNow();
 
   void NotifyICChanged() { any_ic_changed_ = true; }
 
   void AttemptOnStackReplacement(JSFunction* function, int nesting_levels = 1);
 
  private:
   void Optimize(JSFunction* function, const char* reason);
 
   bool CodeSizeOKForOSR(Code* shared_code);
 
   Isolate* isolate_;
 
   bool any_ic_changed_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_RUNTIME_PROFILER_H_