Add blimp to root GN check_targets

blimp/client/feature/render_widget_feature.h

Index: blimp/client/feature/render_widget_feature.h
diff --git a/blimp/client/feature/render_widget_feature.h b/blimp/client/feature/render_widget_feature.h
index 43c5e920a5493a07a1ddd5d186edb4429356c97e..caa417acb814c762c273e87529e0c4ff44744058 100644
--- a/blimp/client/feature/render_widget_feature.h
+++ b/blimp/client/feature/render_widget_feature.h
@@ -12,7 +12,6 @@
 
 #include "base/containers/small_map.h"
 #include "base/macros.h"
-#include "blimp/client/blimp_client_export.h"
 #include "blimp/net/blimp_message_processor.h"
 #include "blimp/net/input_message_generator.h"
 
@@ -38,7 +37,7 @@ namespace client {
 // notified of incoming messages. This class automatically attaches a specific
 // id so that the engine can drop stale RenderWidget related messages after it
 // sends a RenderWidgetMessage::INITIALIZE message.
-class BLIMP_CLIENT_EXPORT RenderWidgetFeature : public BlimpMessageProcessor {
+class RenderWidgetFeature : public BlimpMessageProcessor {
  public:
   // A delegate to be notified of specific RenderWidget related incoming events.
   class RenderWidgetFeatureDelegate {