Move platform abstraction to base library

src/debug.h

Index: src/debug.h
diff --git a/src/debug.h b/src/debug.h
index c295df2654bcf1b30c878d8a900386ba7becd430..e85fbd7a2333151ce1b656a71c333fc102edeef5 100644
--- a/src/debug.h
+++ b/src/debug.h
@@ -8,13 +8,13 @@
 #include "src/allocation.h"
 #include "src/arguments.h"
 #include "src/assembler.h"
+#include "src/base/platform/platform.h"
 #include "src/execution.h"
 #include "src/factory.h"
 #include "src/flags.h"
 #include "src/frames-inl.h"
 #include "src/hashmap.h"
 #include "src/liveedit.h"
-#include "src/platform.h"
 #include "src/string-stream.h"
 #include "src/v8threads.h"
 
@@ -328,7 +328,7 @@ class LockingCommandMessageQueue BASE_EMBEDDED {
  private:
   Logger* logger_;
   CommandMessageQueue queue_;
-  mutable Mutex mutex_;
+  mutable base::Mutex mutex_;
   DISALLOW_COPY_AND_ASSIGN(LockingCommandMessageQueue);
 };
 
@@ -581,7 +581,7 @@ class Debug {
   v8::Debug::MessageHandler message_handler_;
 
   static const int kQueueInitialSize = 4;
-  Semaphore command_received_;  // Signaled for each command received.
+  base::Semaphore command_received_;  // Signaled for each command received.
   LockingCommandMessageQueue command_queue_;
   LockingCommandMessageQueue event_command_queue_;