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When a wheel event listener is added or removed on a page, we set each
layer as having a WheelEventHandlerRegion equal to the entire bounds of
the layer. This happens in Layer::PushPropertiesTo.

This means that when an event listener is changed, we need to cause all
layers to need a push properties and commit. Prior to this CL, this
happens in LayerTreeHost::SetEventListenerProperties by setting
SetNeedsFullTreeSync and SetSubtreePropertyChanged. However, as noted by
surrounding comments, this looks wrong; SetNeedsFullTreeSync only causes
the tree structure to be synced, properties aren't pushed.
SetSubtreePropertyChanged causes a property sync only on the root layer.

This works prior to BGPT because SetNeedsFullTreeSync causes a property
tree rebuild during which all layers are marked as needing a property
push. See PropertyTreeBuilderContext::BuildPropertyTreesInternal which
calls SetLayerPropertyTreeChangedForChild for all child layers as the
tree is built.

When BGPT is turned on, property trees are built in Blink independent of
the layer tree so this doesn't cause us to SetNeedsPushProperties. This
CL fixes SetEventListenerProperties to set the correct flags to
propagate the listener state to the active tree.

This CL fixes:

PointerLockBrowserTest.PointerLockWheelEventRouting
TouchpadPinchBrowserTest.WheelListenerAllowingPinch/0
TouchpadPinchBrowserTest.WheelListenerAllowingPinch/1

With BGPT turned on.

Bug: 912334,881011
Change-Id: I4446ccfd32de12e618219e5fa15c48f5093bcc98
Reviewed-on: https://chromium-review.googlesource.com/c/1369059Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615579}