Reland "Enable libc++ on Android"

base/containers/hash_tables.h

Index: base/containers/hash_tables.h
diff --git a/base/containers/hash_tables.h b/base/containers/hash_tables.h
index d13c46948ed7d5143c890f46f096a008faab8784..5ce9161917269bde566188c88670f00fe1f83483 100644
--- a/base/containers/hash_tables.h
+++ b/base/containers/hash_tables.h
@@ -45,15 +45,9 @@
 #undef __DEPRECATED
 #endif
 
-#if defined(OS_ANDROID)
-#include <hash_map>
-#include <hash_set>
-#define BASE_HASH_IMPL_NAMESPACE std
-#else
 #include <ext/hash_map>
 #include <ext/hash_set>
 #define BASE_HASH_IMPL_NAMESPACE __gnu_cxx
-#endif
 
 #include <string>
 
@@ -84,7 +78,6 @@ struct hash<T*> {
   }
 };
 
-#if !defined(OS_ANDROID)
 // The GNU C++ library provides identity hash functions for many integral types,
 // but not for |long long|.  This hash function will truncate if |size_t| is
 // narrower than |long long|.  This is probably good enough for what we will
@@ -102,7 +95,6 @@ DEFINE_TRIVIAL_HASH(long long);
 DEFINE_TRIVIAL_HASH(unsigned long long);
 
 #undef DEFINE_TRIVIAL_HASH
-#endif  // !defined(OS_ANDROID)
 
 // Implement string hash functions so that strings of various flavors can
 // be used as keys in STL maps and sets.  The hash algorithm comes from the