This is necessary so that various parts of the GPU code do not need to depend on
ui/events.

BUG=686865
TBR=ben@chromium.org

CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2783973002
Cr-Commit-Position: refs/heads/master@{#461475}