[Debugging] Added debugging instrumentation in TouchActionFilter

Right now there's crash at TouchActionFilter when filtering a gesture
scroll update generated by fling controller. This CL adds debugging
instrumentation to record the gesture sequence.

TBR=dtapuska@chromium.org

Bug: 851644
Change-Id: Ifb9b246eab063e1df9563501b7c31d69ae45c16d
Reviewed-on: https://chromium-review.googlesource.com/1191024Reviewed-by: Xida Chen <xidachen@chromium.org>
Commit-Queue: Xida Chen <xidachen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586338}

content/browser/renderer_host/input/touch_action_filter.cc

@@ -85,6 +85,13 @@ FilterGestureEventResult TouchActionFilter::FilterGestureEvent(
       // two-finger scrolling but a "touch-action: pan-x pinch-zoom" region
       // doesn't.
       // TODO(mustaq): Add it to spec?
+      if (!scrolling_touch_action_.has_value()) {
+        static auto* crash_key = base::debug::AllocateCrashKeyString(
+            "scrollupdate-gestures", base::debug::CrashKeySize::Size256);
+        base::debug::SetCrashKeyString(crash_key, gesture_sequence_);
+        base::debug::DumpWithoutCrashing();
+        gesture_sequence_.clear();
+      }
       if (IsYAxisActionDisallowed(scrolling_touch_action_.value())) {
         gesture_event->data.scroll_update.delta_y = 0;
         gesture_event->data.scroll_update.velocity_y = 0;