Make RenderViewTests clean up all RenderViews.

As of crrev.com/c/814994/, the RenderViewTest harness gives tests the
ability to open additional windows, but previously RenderViewTest::TearDown
did not clean up these additional windows, so their WebFrameSchedulerImpls
were not getting destructed during shutdown.

RenderViewTest::TearDown now sends a ViewMsg_Close to all open views.

Bug: 801184
Change-Id: Ibe153b1946bd04c2004904b6df978142be0f7b22
Reviewed-on: https://chromium-review.googlesource.com/866771
Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Yuzu Saijo <yuzus@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Balazs Engedy <engedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#529489}
void RenderViewTest::SendWebGestureEvent(
    const blink::WebGestureEvent& gesture_event) {
  SendInputEvent(gesture_event);
}

void RenderViewTest::SendWebGestureEvent(
    const blink::WebGestureEvent& gesture_event) {
  SendInputEvent(gesture_event);
}
