Export Content Mus for Unit Testing

content/renderer/mus/compositor_mus_connection.h

Index: content/renderer/mus/compositor_mus_connection.h
diff --git a/content/renderer/mus/compositor_mus_connection.h b/content/renderer/mus/compositor_mus_connection.h
index 7b0f69611b6f18388cab81dd709328342bdf3d22..70f8b2dfb3afe620a82aaf6c3e4faa1e07d4e625 100644
--- a/content/renderer/mus/compositor_mus_connection.h
+++ b/content/renderer/mus/compositor_mus_connection.h
@@ -6,11 +6,13 @@
 #define CONTENT_RENDERER_MUS_COMPOSITOR_MUS_CONNECTION_H_
 
 #include "base/bind.h"
+#include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "components/mus/public/cpp/input_event_handler.h"
 #include "components/mus/public/cpp/window.h"
 #include "components/mus/public/cpp/window_tree_connection.h"
 #include "components/mus/public/cpp/window_tree_delegate.h"
+#include "content/common/content_export.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
 
 namespace content {
@@ -23,9 +25,9 @@ class InputHandlerManager;
 // threads. CompositorMusConnection is constructed on the main thread. By
 // default all other methods are assumed to run on the compositor thread unless
 // explicited suffixed with OnMainThread.
-class CompositorMusConnection
-    : public mus::WindowTreeDelegate,
-      public mus::InputEventHandler,
+class CONTENT_EXPORT CompositorMusConnection
+    : NON_EXPORTED_BASE(public mus::WindowTreeDelegate),
+      NON_EXPORTED_BASE(public mus::InputEventHandler),
       public base::RefCountedThreadSafe<CompositorMusConnection> {
  public:
   // Created on main thread.