Fix uninit access in TouchEventQueue

Properly initialize |drop_remaining_touches_in_sequence_| after
its addition in https://codereview.chromium.org/586553002/.

TBR=rbyers@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/581313003

Cr-Commit-Position: refs/heads/master@{#296245}

content/browser/renderer_host/input/touch_event_queue.cc

@@ -374,6 +374,7 @@ TouchEventQueue::TouchEventQueue(TouchEventQueueClient* client,
       dispatching_touch_ack_(NULL),
       dispatching_touch_(false),
       has_handlers_(true),
+      drop_remaining_touches_in_sequence_(false),
       touchmove_slop_suppressor_(new TouchMoveSlopSuppressor(
           config.touchmove_slop_suppression_length_dips)),
       send_touch_events_async_(false),