Use make_unique instead of unique_ptr

In preparation for moving ui/chromeos/ime to
chrome/browser/chromeos/input_method/ui, fix presubmit errors.

Change-Id: I576ef32b13bd74b18a2e942aa6a5b2f0aaa69884
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2228016Reviewed-by: Keith Lee <keithlee@chromium.org>
Commit-Queue: My Nguyen <myy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#775003}

ui/chromeos/ime/infolist_window.cc

@@ -218,8 +218,7 @@ void InfolistWindow::InitWidget() {
       wm::WINDOW_VISIBILITY_ANIMATION_TYPE_FADE);
 
   // BubbleFrameView will be initialized through CreateBubble.
-  GetBubbleFrameView()->SetBubbleBorder(
-      std::unique_ptr<views::BubbleBorder>(new InfolistBorder()));
+  GetBubbleFrameView()->SetBubbleBorder(std::make_unique<InfolistBorder>());
   SizeToContents();
 }