[VK] Remove unused IsKeyboardWindowCreated function.

Not used. Can use |GetKeyboardWindow| to do the same thing (check for
null).

TBR=yhanada@chromium.org

Bug: 845780
Change-Id: I4f104099e92032e25c1aec15c3b67850253ad3e8
Reviewed-on: https://chromium-review.googlesource.com/1124737Reviewed-by: Darren Shen <shend@chromium.org>
Reviewed-by: Yuichiro Hanada <yhanada@chromium.org>
Commit-Queue: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572472}

ui/keyboard/keyboard_controller.cc

@@ -506,10 +506,6 @@ void KeyboardController::ShowKeyboardInDisplay(
   ShowKeyboardInternal(display);
 }
 
-bool KeyboardController::IsKeyboardWindowCreated() {
-  return ui_->HasKeyboardWindow();
-}
-
 void KeyboardController::OnWindowHierarchyChanged(
     const HierarchyChangeParams& params) {
   if (params.new_parent && params.target == GetKeyboardWindow())

ui/keyboard/keyboard_controller.h

@@ -163,9 +163,6 @@ class KEYBOARD_EXPORT KeyboardController
   // Returns true if keyboard is in SHOWN or SHOWING state.
   bool keyboard_visible() const;
 
-  // Returns true if keyboard window has been created.
-  bool IsKeyboardWindowCreated();
-
   // Returns the bounds in screen for the visible portion of the keyboard. An
   // empty rectangle will get returned when the keyboard is hidden.
   const gfx::Rect& visual_bounds_in_screen() const {