Make MockExtensionSystemFactory available in all ExtensionsTests.

extensions/browser/extensions_test.h

Index: extensions/browser/extensions_test.h
diff --git a/extensions/browser/extensions_test.h b/extensions/browser/extensions_test.h
index 3189e27ec8647b6e7b80ea98bdeef71502417b39..e930421a1e1c7fda437e560af79621c16643a393 100644
--- a/extensions/browser/extensions_test.h
+++ b/extensions/browser/extensions_test.h
@@ -9,6 +9,7 @@
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "content/public/test/test_renderer_host.h"
+#include "extensions/browser/mock_extension_system.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace content {
@@ -61,6 +62,8 @@ class ExtensionsTest : public testing::Test {
   // RenderViewHostTester.
   content::RenderViewHostTestEnabler rvh_test_enabler_;
 
+  MockExtensionSystemFactory<MockExtensionSystem> extension_system_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(ExtensionsTest);
 };