Revert of Remove InputMethodEventHandler.

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index 2b64b994637d315ad973e41f5e4382d8bfa6da76..2d36d457672a27fa6712ce10fb719013481a9b5a 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -41,6 +41,7 @@
 #include "ash/frame/custom_frame_view_ash.h"
 #include "ash/gpu_support.h"
 #include "ash/high_contrast/high_contrast_controller.h"
+#include "ash/ime/input_method_event_handler.h"
 #include "ash/keyboard/keyboard_ui.h"
 #include "ash/laser/laser_pointer_controller.h"
 #include "ash/login_status.h"
@@ -620,6 +621,10 @@
   // Please keep in same order as in Init() because it's easy to miss one.
   if (window_modality_controller_)
     window_modality_controller_.reset();
+  if (config != Config::MASH) {
+    RemovePreTargetHandler(
+        window_tree_host_manager_->input_method_event_handler());
+  }
 
   RemovePreTargetHandler(magnifier_key_scroll_handler_.get());
   magnifier_key_scroll_handler_.reset();
@@ -950,6 +955,13 @@
   accelerator_controller_ = shell_port_->CreateAcceleratorController();
   maximize_mode_controller_ = base::MakeUnique<MaximizeModeController>();
 
+  if (!ShouldUseIMEService()) {
+    // Not applicable when using IME service as events are already routed to
+    // InputMethod first.
+    AddPreTargetHandler(
+        window_tree_host_manager_->input_method_event_handler());
+  }
+
   magnifier_key_scroll_handler_ = MagnifierKeyScroller::CreateHandler();
   AddPreTargetHandler(magnifier_key_scroll_handler_.get());
   speech_feedback_handler_ = SpokenFeedbackToggler::CreateHandler();