Switch thread_local to use ThreadPlatformStorage in Android

base/threading/thread_local.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // WARNING: Thread local storage is a bit tricky to get right.  Please make
 // sure that this is really the proper solution for what you're trying to
 // achieve.  Don't prematurely optimize, most likely you can just use a Lock.
 //
 // These classes implement a wrapper around the platform's TLS storage
 // mechanism.  On construction, they will allocate a TLS slot, and free the
 // TLS slot on destruction.  No memory management (creation or destruction) is
 // handled.  This means for uses of ThreadLocalPointer, you must correctly
 // manage the memory yourself, these classes will not destroy the pointer for
 // you.  There are no at-thread-exit actions taken by these classes.
 //
 // ThreadLocalPointer<Type> wraps a Type*.  It performs no creation or
 // destruction, so memory management must be handled elsewhere.  The first call
 // to Get() on a thread will return NULL.  You can update the pointer with a
 // call to Set().
 //
 // ThreadLocalBoolean wraps a bool.  It will default to false if it has never
 // been set otherwise with Set().
 //
 // Thread Safety:  An instance of ThreadLocalStorage is completely thread safe
 // once it has been created.  If you want to dynamically create an instance,
 // you must of course properly deal with safety and race conditions.  This
 // means a function-level static initializer is generally inappropiate.
 //
+// In Android, the system TLS is limited, the implementation is backed with
+// ThreadLocalStorage.
+//
 // Example usage:
 //   // My class is logically attached to a single thread.  We cache a pointer
 //   // on the thread it was created on, so we can implement current().
 //   MyClass::MyClass() {
 //     DCHECK(Singleton<ThreadLocalPointer<MyClass> >::get()->Get() == NULL);
 //     Singleton<ThreadLocalPointer<MyClass> >::get()->Set(this);
 //   }
 //
 //   MyClass::~MyClass() {
 //     DCHECK(Singleton<ThreadLocalPointer<MyClass> >::get()->Get() != NULL);
 //     Singleton<ThreadLocalPointer<MyClass> >::get()->Set(NULL);
 //   }
 //
 //   // Return the current MyClass associated with the calling thread, can be
 //   // NULL if there isn't a MyClass associated.
 //   MyClass* MyClass::current() {
 //     return Singleton<ThreadLocalPointer<MyClass> >::get()->Get();
 //   }
 
 #ifndef BASE_THREADING_THREAD_LOCAL_H_
 #define BASE_THREADING_THREAD_LOCAL_H_
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/threading/thread_local_storage.h"
 
 #if defined(OS_POSIX)
 #include <pthread.h>
 #endif
 
 namespace base {
 namespace internal {
 
 // Helper functions that abstract the cross-platform APIs.  Do not use directly.
 struct BASE_EXPORT ThreadLocalPlatform {
 #if defined(OS_WIN)
   typedef unsigned long SlotType;
+#elif defined(OS_ANDROID)
+  typedef ThreadLocalStorage::StaticSlot SlotType;
 #elif defined(OS_POSIX)
   typedef pthread_key_t SlotType;
 #endif
 
   static void AllocateSlot(SlotType* slot);
   static void FreeSlot(SlotType slot);
   static void* GetValueFromSlot(SlotType slot);
   static void SetValueInSlot(SlotType slot, void* value);
 };
 
@@ skipping 43 matching lines @@
 
  private:
   ThreadLocalPointer<void> tlp_;
 
   DISALLOW_COPY_AND_ASSIGN(ThreadLocalBoolean);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_THREAD_LOCAL_H_