Turns on use_mojo=1 for windows.

chrome/tools/build/win/FILES.cfg

Index: chrome/tools/build/win/FILES.cfg
diff --git a/chrome/tools/build/win/FILES.cfg b/chrome/tools/build/win/FILES.cfg
index 0e96eb1e3cbd11db0583eb92e4e11199f661e8a4..6883f455067782d583db6c484693396457fd7042 100644
--- a/chrome/tools/build/win/FILES.cfg
+++ b/chrome/tools/build/win/FILES.cfg
@@ -306,6 +306,11 @@ FILES = [
     'buildtype': ['dev', 'official'],
   },
   {
+    'filename': 'mojo_system.dll',
+    'buildtype': ['dev', 'official'],
+    'filegroup': ['default', 'symsrc'],
+  },
+  {
     'filename': 'policy_templates.zip',
     'buildtype': ['official'],
     'archive': 'policy_templates.zip',
@@ -567,6 +572,14 @@ FILES = [
     'optional': ['dev'],
   },
   {
+    'filename': 'syzygy/mojo_system.dll',
+    'arch': ['32bit'],
+    'buildtype': ['dev', 'official'],
+    'archive': 'syzygy/mojo_system.dll',
+    'filegroup': ['symsrc'],
+    'optional': ['dev'],
+  },
+  {
     'filename': 'syzygy/syzyasan_rtl.dll',
     'arch': ['32bit'],
     'buildtype': ['dev', 'official'],
@@ -675,6 +688,11 @@ FILES = [
     'archive': 'chrome-win32-syms.zip',
   },
   {
+    'filename': 'mojo_system.dll.pdb',
+    'buildtype': ['dev', 'official'],
+    'archive': 'chrome-win32-syms.zip',
+  },
+  {
     'filename': 'nacl64.exe.pdb',
     'arch': ['32bit'],
     'buildtype': ['dev', 'official'],
@@ -712,6 +730,13 @@ FILES = [
     'optional': ['dev'],
   },
   {
+    'filename': 'syzygy/mojo_system.dll.pdb',
+    'arch': ['32bit'],
+    'buildtype': ['dev', 'official'],
+    'archive': 'chrome-win32-syms.zip',
+    'optional': ['dev'],
+  },
+  {
     'filename': 'syzygy/syzyasan_rtl.dll.pdb',
     'arch': ['32bit'],
     'buildtype': ['dev', 'official'],