Add usage display support for Extension IME.

chrome/browser/chromeos/input_method/input_method_engine.h

 // Copyright (c) 2012 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 CHROME_BROWSER_CHROMEOS_INPUT_METHOD_INPUT_METHOD_ENGINE_H_
 #define CHROME_BROWSER_CHROMEOS_INPUT_METHOD_INPUT_METHOD_ENGINE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 60 matching lines @@
 
     unsigned int modified;
     std::vector<MenuItem> children;
   };
 
   struct InputContext {
     int id;
     std::string type;
   };
 
+  struct UsageEntry {
+    std::string title;
+    std::string body;
+  };
+
   struct Candidate {
     Candidate();
     virtual ~Candidate();
 
     std::string value;
     int id;
     std::string label;
     std::string annotation;
+    UsageEntry usage;
     std::vector<Candidate> candidates;
   };
 
   struct SegmentInfo {
     int start;
     int end;
     SegmentStyle style;
   };
 
   class Observer {
@@ skipping 98 matching lines @@
       const char* engine_id,
       const char* description,
       const char* language,
       const std::vector<std::string>& layouts,
       std::string* error);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_INPUT_METHOD_INPUT_METHOD_ENGINE_H_