Get gn_all/gyp_remaining working for Windows.

This change doesn't actually cause anything new to be built, but it makes 'gn_all' and 'gyp_remaining' exist as targets on a windows build, and explicitly lists all of the targets built on win that weren't listed before.

A number of these targets should actually build in a GN build, but I will take care of that in a follow-up CL.

R=brettw@chromium.org
BUG=354261
CQ_EXTRA_TRYBOTS=tryserver.chromium.linux:android_chromium_gn_compile_dbg,android_chromium_gn_compile_rel;tryserver.chromium.win:win8_chromium_gn_rel,win8_chromium_gn_dbg;tryserver.chromium.mac:mac_chromium_gn_rel,mac_chromium_gn_dbg

Review URL: https://codereview.chromium.org/1064333002

Cr-Commit-Position: refs/heads/master@{#324285}

build/all.gyp

@@ -492,7 +492,7 @@
   ],
   'conditions': [
     # TODO(GYP): make gn_migration.gypi work unconditionally.
-    ['OS=="linux" and target_arch=="x64" and chromeos==0 and chromecast==0 and disable_nacl==0', {
+    ['OS=="win" or (OS=="linux" and target_arch=="x64" and chromeos==0 and chromecast==0 and disable_nacl==0)', {
       'includes': [
         'gn_migration.gypi',
       ],