Implement safepointing of threads

runtime/vm/vm_sources.gypi

 # Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 # This file contains all sources (vm and tests) for the dart virtual machine.
 # Unit test files need to have a '_test' suffix appended to the name.
 {
   'sources': [
     'allocation.cc',
     'allocation.h',
@@ skipping 240 matching lines @@
     'intrinsifier_mips.cc',
     'intrinsifier_x64.cc',
     'isolate.cc',
     'isolate.h',
     'isolate_test.cc',
     'json_stream.h',
     'json_stream.cc',
     'json_test.cc',
     'locations.cc',
     'locations.h',
+    'lockers.cc',
     'lockers.h',
     'log_test.cc',
     'log.cc',
     'log.h',
     'longjump.cc',
     'longjump.h',
     'longjump_test.cc',
     'megamorphic_cache_table.cc',
     'megamorphic_cache_table.h',
     'memory_region.cc',
@@ skipping 106 matching lines @@
     'ring_buffer.h',
     'ring_buffer_test.cc',
     'runtime_entry.h',
     'runtime_entry_list.h',
     'runtime_entry_arm.cc',
     'runtime_entry_arm64.cc',
     'runtime_entry_ia32.cc',
     'runtime_entry_mips.cc',
     'runtime_entry.cc',
     'runtime_entry_x64.cc',
+    'safepoint.cc',
+    'safepoint.h',
     'scanner.cc',
     'scanner.h',
     'scanner_test.cc',
     'scavenger.cc',
     'scavenger.h',
     'scavenger_test.cc',
     'scope_timer.h',
     'scopes.cc',
     'scopes.h',
     'scopes_test.cc',
@@ skipping 105 matching lines @@
     'vtune.h',
     'weak_code.cc',
     'weak_code.h',
     'weak_table.cc',
     'weak_table.h',
     'zone.cc',
     'zone.h',
     'zone_test.cc',
   ],
 }