Add --keyboard-usability-test flag and always show keyboard unless manually hide

chrome/browser/ui/ash/ash_keyboard_controller_proxy.cc

Index: chrome/browser/ui/ash/ash_keyboard_controller_proxy.cc
diff --git a/chrome/browser/ui/ash/ash_keyboard_controller_proxy.cc b/chrome/browser/ui/ash/ash_keyboard_controller_proxy.cc
index 9c986f6ae936a23f1b7a35ef9a633d7b55c88ea1..b3ecaebf0ee53756c0ca8266cc0cf3795b86be9f 100644
--- a/chrome/browser/ui/ash/ash_keyboard_controller_proxy.cc
+++ b/chrome/browser/ui/ash/ash_keyboard_controller_proxy.cc
@@ -148,9 +148,13 @@ void AshKeyboardControllerProxy::ShowKeyboardContainer(
     NOTIMPLEMENTED();
 
   KeyboardControllerProxy::ShowKeyboardContainer(container);
-  gfx::Rect showing_area =
-      ash::DisplayController::GetPrimaryDisplay().work_area();
-  GetInputMethod()->GetTextInputClient()->EnsureCaretInRect(showing_area);
+  // GetTextInputClient may return NULL when keyboard-usability-test flag is
+  // set.
+  if (GetInputMethod()->GetTextInputClient()) {
+    gfx::Rect showing_area =
+        ash::DisplayController::GetPrimaryDisplay().work_area();
+    GetInputMethod()->GetTextInputClient()->EnsureCaretInRect(showing_area);
+  }
 }
 
 void AshKeyboardControllerProxy::SetUpdateInputType(ui::TextInputType type) {