Add usage stats entries about how many times keyboard are expanded/folded

This CL introduces a pair of new usage stats entries so that we can know how many times the keyboard are expanded/folded on Android.

No visible change is intended.

Patch from Tsuyoshi Matsuzaki.

BUG=none
TEST=compile


git-svn-id: http://mozc.googlecode.com/svn/trunk/src/session@446 a6090854-d499-a067-5803-1114d4e51264
diff --git a/commands.proto b/commands.proto
index ea6727f..869b284 100644
--- a/commands.proto
+++ b/commands.proto
@@ -479,6 +479,8 @@
     SUBMITTED_CANDIDATE_ROW_8 = 17;
     SUBMITTED_CANDIDATE_ROW_9 = 18;
     SUBMITTED_CANDIDATE_ROW_GE10 = 19;
+    KEYBOARD_FOLD_EVENT = 20;
+    KEYBOARD_EXPAND_EVENT = 21;
   }
   optional UsageStatsEvent usage_stats_event = 7;
   optional int32 usage_stats_event_int_value = 9;
diff --git a/session_usage_observer.cc b/session_usage_observer.cc
index 3a2dfc3..859bb92 100644
--- a/session_usage_observer.cc
+++ b/session_usage_observer.cc
@@ -361,6 +361,12 @@
     case commands::SessionCommand::SUBMITTED_CANDIDATE_ROW_GE10:
       UsageStats::IncrementCount("SubmittedCandidateRowGE10");
       break;
+    case commands::SessionCommand::KEYBOARD_FOLD_EVENT:
+      UsageStats::IncrementCount("KeyboardFoldEvent");
+      break;
+    case commands::SessionCommand::KEYBOARD_EXPAND_EVENT:
+      UsageStats::IncrementCount("KeyboardExpandEvent");
+      break;
     default:
       LOG(WARNING) << "client side usage stats event has invalid category";
       break;