One-liner cl to include set

git cl lint pointed TouchSelectionControllerImpl should include set.

Bug: None
Test: Build.
Change-Id: I8b78fbf36092116e35e287edb96557fc9be9f70d
Reviewed-on: https://chromium-review.googlesource.com/c/1297247Reviewed-by: Mohsen Izadi <mohsen@chromium.org>
Commit-Queue: David Jacobo <djacobo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602390}

ui/views/touchui/touch_selection_controller_impl.cc

@@ -4,6 +4,8 @@
 
 #include "ui/views/touchui/touch_selection_controller_impl.h"
 
+#include <set>
+
 #include "base/metrics/histogram_macros.h"
 #include "base/time/time.h"
 #include "ui/aura/client/cursor_client.h"