Preserve tap-count when a gesture double-tap becomes a gesture-tap.

When a double-tap is dropped through a touch-action (e.g.  "none" or
"manipulation"), we replace the double-tap event with a single-tap which
is the second single-tap in the gesture sequence.  Blink dispatches
compat "click" events for both these taps.  Without a correct tap-count
(==2) in the second tap, a follow-up "dblclick" event is not dispatched,
which is wrong.  This CL fixes the problem.

Bug: 874474
Change-Id: I25f9806e5ec9f211f9f83d59e8949052a816aaf3
Reviewed-on: https://chromium-review.googlesource.com/c/1276846Reviewed-by: Xida Chen <xidachen@chromium.org>
Reviewed-by: Navid Zolghadr <nzolghadr@chromium.org>
Commit-Queue: Mustaq Ahmed <mustaq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598928}

content/browser/renderer_host/input/touch_action_filter.cc

@@ -129,14 +129,23 @@ FilterGestureEventResult TouchActionFilter::FilterGestureEvent(
                  ? FilterGestureEventResult::kFilterGestureEventFiltered
                  : FilterGestureEventResult::kFilterGestureEventAllowed;
 
-    // The double tap gesture is a tap ending event. If a double tap gesture is
-    // filtered out, replace it with a tap event.
+    // The double tap gesture is a tap ending event. If a double-tap gesture is
+    // filtered out, replace it with a tap event but preserve the tap-count to
+    // allow firing dblclick event in Blink.
+    //
+    // TODO(mustaq): This replacement of a double-tap gesture with a tap seems
+    // buggy, it produces an inconsistent gesture event stream: GestureTapCancel
+    // followed by GestureTap.  See crbug.com/874474#c47 for a repro.  We don't
+    // know of any bug resulting from it, but it's better to fix the broken
+    // assumption here at least to avoid introducing new bugs in future.
     case WebInputEvent::kGestureDoubleTap:
       gesture_sequence_in_progress_ = false;
       gesture_sequence_.append("D");
       DCHECK_EQ(1, gesture_event->data.tap.tap_count);
-      if (!allow_current_double_tap_event_)
+      if (!allow_current_double_tap_event_) {
         gesture_event->SetType(WebInputEvent::kGestureTap);
+        gesture_event->data.tap.tap_count = 2;
+      }
       allow_current_double_tap_event_ = true;
       break;
 

content/browser/renderer_host/input/touch_action_filter_unittest.cc

@@ -828,6 +828,7 @@ TEST_F(TouchActionFilterTest, DoubleTap) {
   EXPECT_EQ(filter_.FilterGestureEvent(&double_tap),
             FilterGestureEventResult::kFilterGestureEventAllowed);
   EXPECT_EQ(WebInputEvent::kGestureTap, double_tap.GetType());
+  EXPECT_EQ(2, double_tap.data.tap.tap_count);
   filter_.DecreaseActiveTouches();
 }