Output warning when the container window doesn't exist unexpectedly

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 676da64d047e71106edad66bed6ce9436923b5f1..48cc52020d9cf07abdb0a6fba30669e0839df61f 100644
--- a/ui/keyboard/keyboard_controller.cc
+++ b/ui/keyboard/keyboard_controller.cc
@@ -406,8 +406,11 @@ void KeyboardController::OnShowImeIfNeeded() {
 }
 
 void KeyboardController::ShowKeyboardInternal(int64_t display_id) {
-  if (!container_.get())
+  DCHECK(container_.get());
+  if (!container_.get()) {
+    LOG(WARNING) << "container_ was not initialized unexpectedly.";

[bshe, 2017/04/10 13:38:37]

If you have a DCHECK, you shouldn't need to handle its failure:
https://chromium.googlesource.com/chromium/src/+/master/styleguide/c++/c++.md...

If container_.get() can't be null, perhaps remove the if check?

[oka, 2017/04/13 09:07:57]

Done. I added DCHECK only and commened the rationale why the window should exist
there.

     return;
+  }
 
   if (container_->children().empty()) {
     keyboard::MarkKeyboardLoadStarted();