Updates the histograms for IMF and IMEs according to the new design.

chrome/browser/chromeos/input_method/input_method_manager_impl.h

Index: chrome/browser/chromeos/input_method/input_method_manager_impl.h
diff --git a/chrome/browser/chromeos/input_method/input_method_manager_impl.h b/chrome/browser/chromeos/input_method/input_method_manager_impl.h
index 1aa0123660229e22fd2ff9080b16502a0ed28ccf..88640007d3765c930f15f2fb6c888a49ffdf5ac3 100644
--- a/chrome/browser/chromeos/input_method/input_method_manager_impl.h
+++ b/chrome/browser/chromeos/input_method/input_method_manager_impl.h
@@ -222,6 +222,9 @@ class InputMethodManagerImpl : public InputMethodManager,
   // If state is active, active input method is updated.
   void ReconfigureIMFramework(StateImpl* state);
 
+  // Record input method usage histograms.
+  void RecordInputMethodUsage(std::string input_method_id);
+
   scoped_ptr<InputMethodDelegate> delegate_;
 
   // The current UI session status.
@@ -256,6 +259,16 @@ class InputMethodManagerImpl : public InputMethodManager,
   typedef std::map<std::string, InputMethodEngineInterface*> EngineMap;
   EngineMap engine_map_;
 
+  // The map from input method id to the input method stat id.
+  // The stat id has the format: <category#><first char after prefix><index>
+  // For example, Chinese Simplified Pinyin IME has the stat id:
+  //   2,'p',1 -> 211201
+  //   2 means it in INPUT_METHOD_CATEGORY_ZH;
+  //   112 means the first char after prefix is 'p' of 'pinyin';

[Ilya Sherman, 2014/09/16 21:51:48]

I assume you're restricting only to lower ASCII characters -- is that true?  If
so, it would probably be more convenient to use an index in the  range 0 to 25
(or 1 to 26), rather than the raw ASCII value.

[Shu Chen, 2014/09/17 15:17:28]

I'm not using range of 0 to 25 because it can be digit. e.g. "hangul_2set".

+  //   01 means it's the second pinyin as the first pinyin is for Traditional
+  //   Chinese Pinyin IME. Note "zh-hant-t-i0-pinyin" < "zh-t-i0-pinyin".
+  std::map<std::string, int> stat_id_map_;
+
   DISALLOW_COPY_AND_ASSIGN(InputMethodManagerImpl);
 };