Fix official build due to 2x.pak reference

My Metro/HiDPI change (r133613) broke the official build. The problem was that I was referencing the new 2x pak files but they aren't created by default yet.

Fix was to mark the references as optional.

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/10207021

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@133939 0039d316-1c4b-4281-b951-d872f2087c98

chrome/tools/build/win/FILES.cfg

@@ -351,16 +351,29 @@ FILES = [
     'arch': ['32bit', '64bit'],
     'buildtype': ['dev', 'official'],
   },
+  {
+    'filename': 'theme_resources_2x.pak',
+    'arch': ['32bit', '64bit'],
+    'buildtype': ['dev', 'official'],
+    'optional': ['dev', 'official'],
+  },
   {
     'filename': 'theme_resources_metro_1x.pak',
     'arch': ['32bit', '64bit'],
     'buildtype': ['dev', 'official'],
+    'optional': ['dev', 'official'],
   },
   {
     'filename': 'ui_resources_standard.pak',
     'arch': ['32bit', '64bit'],
     'buildtype': ['dev', 'official'],
   },
+  {
+    'filename': 'ui_resources_2x.pak',
+    'arch': ['32bit', '64bit'],
+    'buildtype': ['dev', 'official'],
+    'optional': ['dev', 'official'],
+  },
   {
     'filename': 'wow_helper.exe',
     'arch': ['32bit', '64bit'],