Isolate extensions_unittests.

BUG=98637

Review URL: https://codereview.chromium.org/1213943002

Cr-Commit-Position: refs/heads/master@{#336928}
diff --git a/extensions/extensions_tests.gyp b/extensions/extensions_tests.gyp
index 80f8688..8703f29 100644
--- a/extensions/extensions_tests.gyp
+++ b/extensions/extensions_tests.gyp
@@ -126,6 +126,19 @@
             'extensions_browsertests.isolate',
           ],
         },
+        {
+          'target_name': 'extensions_unittests_run',
+          'type': 'none',
+          'dependencies': [
+            'extensions_unittests',
+          ],
+          'includes': [
+            '../build/isolate.gypi',
+          ],
+          'sources': [
+            'extensions_unittests.isolate',
+          ],
+        }
       ],
     }],
   ],