Fix GN bootstrap.

Added missing files.

BUG=none
R=jochen@chromium.org, thakis@chromium.org

Review-Url: https://codereview.chromium.org/2747483002
Cr-Commit-Position: refs/heads/master@{#456229}

tools/gn/bootstrap/bootstrap.py

@@ -384,6 +384,7 @@ def write_gn_ninja(path, root_gen_dir, options):
       'base/base_paths.cc',
       'base/base_switches.cc',
       'base/build_time.cc',
+      'base/callback_helpers.cc',
       'base/callback_internal.cc',
       'base/command_line.cc',
       'base/debug/activity_tracker.cc',
@@ -605,6 +606,7 @@ def write_gn_ninja(path, root_gen_dir, options):
         'base/allocator/allocator_shim.cc',
         'base/allocator/allocator_shim_default_dispatch_to_glibc.cc',
         'base/memory/shared_memory_posix.cc',
+        'base/memory/shared_memory_tracker.cc',
         'base/nix/xdg_util.cc',
         'base/process/internal_linux.cc',
         'base/process/memory_linux.cc',