Isolate check_internal.py to the .gypi files that need it.

chrome/chrome_tests_unit.gypi

Index: chrome/chrome_tests_unit.gypi
diff --git a/chrome/chrome_tests_unit.gypi b/chrome/chrome_tests_unit.gypi
index 263a7efa941360bf81df6fb935a1bcb84ac51f87..5d7b7f7b50b95b1013a2dac2908d9c9ef9e8f89b 100644
--- a/chrome/chrome_tests_unit.gypi
+++ b/chrome/chrome_tests_unit.gypi
@@ -414,6 +414,11 @@
         'chrome_resources.gyp:chrome_resources',
         'chrome_resources.gyp:chrome_strings',
       ],
+      # TODO(joi): Remove this section once the google_apis tests are
+      # a separate unit test binary.
+      'includes': [
+        '../google_apis/determine_use_official_keys.gypi',
+      ],
       'include_dirs': [
         '..',
       ],
@@ -2268,11 +2273,6 @@
             ['exclude', '^browser/importer/'],
           ],
         }],
-        # TODO(joi): Remove from this file once separate
-        # google_apis_unittests target is established.
-        ['use_official_google_api_keys==1', {
-          'defines': ['USE_OFFICIAL_GOOGLE_API_KEYS=1'],
-        }],
         ['enable_managed_users!=1', {
           'sources/': [
             ['exclude', '^browser/managed_mode/'],