Do not set touch action to Auto at GSB if it is already set

In chrome VR or virtual keyboard case, we can get GestureScrollBegin
without GestureTapDown, and that |scrolling_touch_action_| may have no
value. In this case, we set it to Auto to prevent crash. This was done
in a previous CL:
https://chromium-review.googlesource.com/c/chromium/src/+/1195649

However, there was a small mistake in the previous CL. That is, the
|scrolling_touch_action_| could have been set when the browser receives
the ACK for the touch start from the main thread. In this case, we should
not set it to Auto.

Bug: 880701
Change-Id: I250bb7a09840f16665cfcf5826236cad99b533c5
Reviewed-on: https://chromium-review.googlesource.com/1213502Reviewed-by: Navid Zolghadr <nzolghadr@chromium.org>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Commit-Queue: Xida Chen <xidachen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590059}

content/browser/renderer_host/input/touch_action_filter.cc

@@ -55,10 +55,12 @@ FilterGestureEventResult TouchActionFilter::FilterGestureEvent(
   switch (gesture_event->GetType()) {
     case WebInputEvent::kGestureScrollBegin: {
       DCHECK(!suppress_manipulation_events_);
-      // In VR, GestureScrollBegin could come without GestureTapDown.
+      // In VR or virtual keyboard (https://crbug.com/880701),
+      // GestureScrollBegin could come without GestureTapDown.
       if (!gesture_sequence_in_progress_) {
         gesture_sequence_in_progress_ = true;
-        SetTouchAction(cc::kTouchActionAuto);
+        if (!scrolling_touch_action_.has_value())
+          SetTouchAction(cc::kTouchActionAuto);
       }
       gesture_sequence_.append("B");
       if (!scrolling_touch_action_.has_value()) {

content/browser/renderer_host/input/touch_action_filter_unittest.cc

@@ -1149,6 +1149,20 @@ TEST_F(TouchActionFilterTest, ScrollBeginWithoutTapDown) {
   EXPECT_EQ(filter_.allowed_touch_action().value(), cc::kTouchActionAuto);
 }
 
+TEST_F(TouchActionFilterTest, ScrollBeginWithoutTapDownWithKnownTouchAction) {
+  filter_.OnHasTouchEventHandlers(true);
+  EXPECT_FALSE(ScrollingTouchAction().has_value());
+  EXPECT_FALSE(filter_.allowed_touch_action().has_value());
+
+  filter_.OnSetTouchAction(cc::kTouchActionPan);
+  WebGestureEvent scroll_begin =
+      SyntheticWebGestureEventBuilder::BuildScrollBegin(5, 0, kSourceDevice);
+  EXPECT_EQ(filter_.FilterGestureEvent(&scroll_begin),
+            FilterGestureEventResult::kFilterGestureEventAllowed);
+  EXPECT_EQ(ScrollingTouchAction().value(), cc::kTouchActionPan);
+  EXPECT_EQ(filter_.allowed_touch_action().value(), cc::kTouchActionPan);
+}
+
 TEST_F(TouchActionFilterTest, TouchpadScroll) {
   WebGestureEvent scroll_begin =
       SyntheticWebGestureEventBuilder::BuildScrollBegin(