Revert of Remove InputMethodEventHandler.

ash/display/window_tree_host_manager.cc

Index: ash/display/window_tree_host_manager.cc
diff --git a/ash/display/window_tree_host_manager.cc b/ash/display/window_tree_host_manager.cc
index 4a1629e38721c3270d340ee01df80060f11fc5be..b562c761315c556838ff12ffd4b825157d70b1b7 100644
--- a/ash/display/window_tree_host_manager.cc
+++ b/ash/display/window_tree_host_manager.cc
@@ -17,6 +17,7 @@
 #include "ash/host/ash_window_tree_host.h"
 #include "ash/host/ash_window_tree_host_init_params.h"
 #include "ash/host/root_window_transformer.h"
+#include "ash/ime/input_method_event_handler.h"
 #include "ash/magnifier/magnification_controller.h"
 #include "ash/magnifier/partial_magnification_controller.h"
 #include "ash/public/cpp/config.h"
@@ -839,8 +840,11 @@
       // Ash uses singleton InputMethod and it won't call OnFocus/OnBlur when
       // the active window changed.
       input_method_->OnFocus();
+      input_method_event_handler_.reset(
+          new InputMethodEventHandler(input_method_.get()));
     }
     host->SetSharedInputMethod(input_method_.get());
+    ash_host->set_input_method_handler(input_method_event_handler_.get());
   }
 
   host->window()->SetName(base::StringPrintf(