[VK] Simplify KeyboardController::SetDraggableArea.

|SetDraggableArea| returns checks if the container behavior is null,
but KeyboardController always has a container behavior (initialised in
the constructor).

This patch removes the container behavior null check.

Bug: 845780
Change-Id: Iaa21bd8179a7fb88a0dd277f4888ae778c624d99
Reviewed-on: https://chromium-review.googlesource.com/1069950
Commit-Queue: Darren Shen <shend@chromium.org>
Reviewed-by: Yuichiro Hanada <yhanada@chromium.org>
Cr-Commit-Position: refs/heads/master@{#560995}

ui/keyboard/keyboard_controller.cc

@@ -848,10 +848,7 @@ void KeyboardController::SetContainerType(
 }
 
 bool KeyboardController::SetDraggableArea(const gfx::Rect& rect) {
-  if (container_behavior_) {
-    return container_behavior_->SetDraggableArea(rect);
-  }
-  return false;
+  return container_behavior_->SetDraggableArea(rect);
 }
 
 bool KeyboardController::DisplayVirtualKeyboard() {

ui/keyboard/keyboard_controller.h

@@ -190,7 +190,7 @@ class KEYBOARD_EXPORT KeyboardController
                         base::Optional<gfx::Rect> target_bounds,
                         base::OnceCallback<void(bool)> callback);
 
-  // Sets floating keyboard drggable rect.
+  // Sets floating keyboard draggable rect.
   bool SetDraggableArea(const gfx::Rect& rect);
 
   void MoveToDisplayWithTransition(display::Display display,