Deduplicate PlatformThread's POSIX implementations of SetThreadPriority.

base/base.gypi

Index: base/base.gypi
diff --git a/base/base.gypi b/base/base.gypi
index 13cba85da1693ba18a59fd5efa877aff100ddbaf..44b79772247b8021c028e97aec70b0aa5d1f9bcb 100644
--- a/base/base.gypi
+++ b/base/base.gypi
@@ -602,6 +602,8 @@
           'threading/non_thread_safe_impl.h',
           'threading/platform_thread.h',
           'threading/platform_thread_android.cc',
+          'threading/platform_thread_internal_posix.cc',
+          'threading/platform_thread_internal_posix.h',
           'threading/platform_thread_linux.cc',
           'threading/platform_thread_mac.mm',
           'threading/platform_thread_posix.cc',
@@ -896,6 +898,7 @@
               ['include', '^process/.*_ios\.(cc|mm)$'],
               ['include', '^process/memory_stubs\.cc$'],
               ['include', '^process/process_handle_posix\.cc$'],
+              ['exclude', '^threading/platform_thread_internal_posix\\.(h|cc)'],
               ['exclude', 'files/file_path_watcher_fsevents.cc'],
               ['exclude', 'files/file_path_watcher_fsevents.h'],
               ['include', 'files/file_path_watcher_mac.cc'],
@@ -963,10 +966,11 @@
           }],
           ['(OS == "mac" or OS == "ios") and >(nacl_untrusted_build)==0', {
             'sources/': [
-              ['exclude', '^files/file_path_watcher_stub\\.cc$'],
               ['exclude', '^base_paths_posix\\.cc$'],
+              ['exclude', '^files/file_path_watcher_stub\\.cc$'],
               ['exclude', '^native_library_posix\\.cc$'],
               ['exclude', '^strings/sys_string_conversions_posix\\.cc$'],
+              ['exclude', '^threading/platform_thread_internal_posix\\.cc$'],
             ],
           }],
           ['<(os_bsd)==1 and >(nacl_untrusted_build)==0', {