[VizHitTesting] Skip checking nested iframe when one iframe is marked as kHitTestAsk

When we have nested main_frame->parent_frame->child_frame and only the
mid-level parent_frame has kHitTestAsk flag, we should not directly
dispatch the event to the child_frame because the parent_frame may have
overlapping regions with main_frame divs. Instead RWHIER should always
ask when it encounters a mid-level kHitTestAsk flag.

To fix the drag and drop issue (crbug.com/804633) in V1, the logic above
was broken as a temporary workaround. Now that the drag and drop bug has
been formally fixed, we should resume the correct logic.

Bug: 995850
Change-Id: Idc380b0249e650d3b73af60f2a1d99f30bee1a3b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1762531Reviewed-by: Robert Kroeger <rjkroege@chromium.org>
Commit-Queue: Yi Gu <yigu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#688771}

components/viz/host/hit_test/hit_test_query.cc

@@ -231,9 +231,8 @@ bool HitTestQuery::FindTargetInRegionForLocation(
   DCHECK_EQ(!!(flags & HitTestRegionFlags::kHitTestAsk),
             !!hit_test_data_[region_index].async_hit_test_reasons);
 
-  if (features::IsVizHitTestingSurfaceLayerEnabled() &&
-      ((flags & HitTestRegionFlags::kHitTestAsk) &&
-       !(flags & HitTestRegionFlags::kHitTestIgnore))) {
+  if ((flags & HitTestRegionFlags::kHitTestAsk) &&
+      !(flags & HitTestRegionFlags::kHitTestIgnore)) {
     target->frame_sink_id = hit_test_data_[region_index].frame_sink_id;
     target->location_in_target = location_in_target;
     target->flags = flags;
@@ -260,8 +259,7 @@ bool HitTestQuery::FindTargetInRegionForLocation(
   if (!RegionMatchEventSource(event_source, flags))
     return false;
 
-  if ((flags &
-       (HitTestRegionFlags::kHitTestMine | HitTestRegionFlags::kHitTestAsk)) &&
+  if ((flags & HitTestRegionFlags::kHitTestMine) &&
       !(flags & HitTestRegionFlags::kHitTestIgnore)) {
     target->frame_sink_id = hit_test_data_[region_index].frame_sink_id;
     target->location_in_target = location_in_target;

components/viz/host/hit_test/hit_test_query_unittest.cc

@@ -1090,14 +1090,15 @@ TEST_F(HitTestQueryTest, ChildHitTestAskFlag) {
                                HitTestRegionFlags::kHitTestMouse);
 }
 
-// One embedder with nested OOPIFs.
+// One embedder with nested OOPIFs. When the mid-level iframe has kHitTestAsk
+// flag we should do async hit test and skip checking its descendants.
 //
 //  +e-------------+
 //  |   +c---------|     Point   maps to
 //  | 1 |    2     |     -----   -------
 //  |   |          |       1        e
 //  |   |+b--------|       2        c
-//  |   ||         |       3        b
+//  |   ||         |       3        c
 //  |   ||   3     |
 //  +--------------+
 //
@@ -1143,17 +1144,21 @@ TEST_F(HitTestQueryTest, NestedOOPIFs) {
   Target target2 =
       hit_test_query().FindTargetForLocation(EventSource::MOUSE, point2);
   EXPECT_EQ(target2.frame_sink_id, c_id);
+  // point2 + transform_e_to_c  = (2, 2).
   EXPECT_EQ(target2.location_in_target, gfx::PointF(2, 2));
   EXPECT_EQ(target2.flags, HitTestRegionFlags::kHitTestChildSurface |
                                HitTestRegionFlags::kHitTestAsk |
                                HitTestRegionFlags::kHitTestMouse);
 
-  // b is the deepest OOPIF for point3, return b with ask flag.
+  // b is the deepest OOPIF for point3, but c has the ask flag. Return c
+  // accordingly.
   Target target3 =
       hit_test_query().FindTargetForLocation(EventSource::MOUSE, point3);
-  EXPECT_EQ(target3.frame_sink_id, b_id);
-  EXPECT_EQ(target3.location_in_target, gfx::PointF(2, 2));
-  EXPECT_EQ(target3.flags, HitTestRegionFlags::kHitTestAsk |
+  EXPECT_EQ(target3.frame_sink_id, c_id);
+  // point3 + transform_e_to_c  = (2, 102).
+  EXPECT_EQ(target3.location_in_target, gfx::PointF(2, 102));
+  EXPECT_EQ(target3.flags, HitTestRegionFlags::kHitTestChildSurface |
+                               HitTestRegionFlags::kHitTestAsk |
                                HitTestRegionFlags::kHitTestMouse);
 }