Add a FakeImeFeatureDelegate to the Linux client.

blimp/client/feature/tab_control_feature.h

Index: blimp/client/feature/tab_control_feature.h
diff --git a/blimp/client/feature/tab_control_feature.h b/blimp/client/feature/tab_control_feature.h
index 00f21696e0787cf06b85bf2b846057840709dd8a..962d0c2d57b8526fcaa912e5bce0f3028a588451 100644
--- a/blimp/client/feature/tab_control_feature.h
+++ b/blimp/client/feature/tab_control_feature.h
@@ -35,11 +35,11 @@ class TabControlFeature : public BlimpMessageProcessor {
   void CreateTab(int tab_id);
   void CloseTab(int tab_id);
 
- private:
   // BlimpMessageProcessor implementation.
   void ProcessMessage(std::unique_ptr<BlimpMessage> message,
                       const net::CompletionCallback& callback) override;
 
+ private:
   // Used to send BlimpMessage::TAB_CONTROL messages to the engine.
   std::unique_ptr<BlimpMessageProcessor> outgoing_message_processor_;