[Contextual Search] Add Mojo-enabled API component.

components/contextual_search/contextual_search_ui_handle.h

Index: components/contextual_search/contextual_search_ui_handle.h
diff --git a/components/contextual_search/contextual_search_ui_handle.h b/components/contextual_search/contextual_search_ui_handle.h
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+++ b/components/contextual_search/contextual_search_ui_handle.h
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+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_CONTEXTUAL_SEARCH_CONTEXTUAL_SEARCH_UI_HANDLE_H_
+#define COMPONENTS_CONTEXTUAL_SEARCH_CONTEXTUAL_SEARCH_UI_HANDLE_H_
+
+#include <string>
+
+#include "base/macros.h"
+
+namespace contextual_search {
+
+// Interface that the Contextual Search Renderer API uses to call back to
+// the browser.
+class ContextualSearchUIHandle {
+ public:
+  ContextualSearchUIHandle() {}
+  virtual ~ContextualSearchUIHandle() {}
+
+  // Set the caption in the Contextual Search Bar.
+  virtual void SetCaption(std::string caption) = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ContextualSearchUIHandle);
+};
+
+}  // namespace contextual_search
+
+#endif  // COMPONENTS_CONTEXTUAL_SEARCH_CONTEXTUAL_SEARCH_UI_HANDLE_H_