Exclude chrome/common/extensions/api/ from build if enable_extensions==0

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 7487fb99ae2938ab4585c760b7295bd4e7646a59..d0a09ac76bebe3311a9d889a74eedbac27a9285d 100644
--- a/chrome/chrome_tests_unit.gypi
+++ b/chrome/chrome_tests_unit.gypi
@@ -1729,6 +1729,7 @@
           'sources/': [
             ['exclude', '^browser/extensions/api/'],
             ['exclude', '^browser/sync/glue/chrome_extensions_activity_monitor_unittest.cc'],
+            ['exclude', '^common/extensions/api/'],
           ],
         }],
         ['use_ash==1', {