Env: win7, GN args:
==========================
is_component_build = false                                                      
is_asan = false   
is_debug = true                                                                 
enable_nacl = true
enable_package_mash_services = true
==========================

The compile output:
==========================
D:\src\cr3\src>ninja -C out\TDebug chrome_child
ninja: Entering directory `out\TDebug'
[45/45] LINK(DLL) chrome_child.dll chrome_child.dll.lib
FAILED: d:/depot_tools/python276_bin/python.exe gyp-win-tool link-wrapper environment.x64 False link.exe /nologo /IMPLIB:./chrome_child.dll.lib /DLL /OUT:./chro
me_child.dll /PDB:./chrome_child.dll.pdb @./chrome_child.dll.rsp
chrome_main.obj : error LNK2019: unresolved external symbol "int __cdecl MashMain(void)" (?MashMain@@YAHXZ) referenced in function ChromeMain
./chrome_child.dll : fatal error LNK1120: 1 unresolved externals
ninja: build stopped: subcommand failed.