Make IME extensions decide when to show the keyboard.

ui/keyboard/keyboard_controller.cc

Index: ui/keyboard/keyboard_controller.cc
diff --git a/ui/keyboard/keyboard_controller.cc b/ui/keyboard/keyboard_controller.cc
index fa52b2add4fe432f747fd09dec87fd7b4f03f465..674685b2658514392b3234f1774866e98b647261 100644
--- a/ui/keyboard/keyboard_controller.cc
+++ b/ui/keyboard/keyboard_controller.cc
@@ -306,6 +306,10 @@ void KeyboardController::ShowKeyboardInDisplay(int64_t display_id) {
   ShowKeyboardInternal(display_id);
 }
 
+bool KeyboardController::IsKeyboardWindowCreated() {
+  return keyboard_container_initialized() && ui_->HasKeyboardWindow();
+}
+
 void KeyboardController::OnWindowHierarchyChanged(
     const HierarchyChangeParams& params) {
   if (params.new_parent && params.target == container_.get())