The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/db6961c90d381c41b504bbe86a3ce493637a8aa3

commit db6961c90d381c41b504bbe86a3ce493637a8aa3
Author: David Bokan <bokan@chromium.org>
Date: Thu Jan 11 18:51:49 2018

Make scroll element id SetNeedsCommit

Currently, a scrollbar layer getting a new scroll element id marks the
tree as needing a full tree sync. This seems somewhat overkill as this
(by itself) doesn't cause any changes to the tree structure. Worse, this
only marks the _structure_ of the tree as needing to be synced. It
doesn't mark the layer as needing to push its properties across the
commit. So if the layer doesn't need to push properties for any other
reasons, the new scroll element id wouldn't get committed to the impl
side layer!

Some code archaeology shows this goes all the way back to
https://crrev.com/0bf9472475c27b921b18c55dad34f9d7ad15d18e. At that
time, it looks like a tree sync also pushed all properties so at some
point this was optimized out. We typically don't notice as changing a
scrolling layer on a scrollbar doesn't really happen today. This is
changing with document.rootScroller since the viewport scrollbars can be
reparented to the new rootScroller. This can cause a crash when the impl
side scrollbar layers have an invalid scroll element id after a commit.

This CL changes the SetScrollElementId on each type of scrollbar layer
to call SetNeedsCommit instead of SetNeedsFullTreeSync. SetNeedsCommit
calls SetNeedsPushProperties on the layer so the scroll element id is
now committed.

Bug:  773362 
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel
Change-Id: I3387e71a4de44fb24d2911b2900299cc1842334c
Reviewed-on: https://chromium-review.googlesource.com/861323
Reviewed-by: enne <enne@chromium.org>
Commit-Queue: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#528686}
[modify] https://crrev.com/db6961c90d381c41b504bbe86a3ce493637a8aa3/cc/layers/painted_overlay_scrollbar_layer.cc
[modify] https://crrev.com/db6961c90d381c41b504bbe86a3ce493637a8aa3/cc/layers/painted_scrollbar_layer.cc
[modify] https://crrev.com/db6961c90d381c41b504bbe86a3ce493637a8aa3/cc/layers/scrollbar_layer_impl_base.h
[modify] https://crrev.com/db6961c90d381c41b504bbe86a3ce493637a8aa3/cc/layers/scrollbar_layer_unittest.cc
[modify] https://crrev.com/db6961c90d381c41b504bbe86a3ce493637a8aa3/cc/layers/solid_color_scrollbar_layer.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e1bfa83b72c16ce19270d8e5641aa2bc46447b37

commit e1bfa83b72c16ce19270d8e5641aa2bc46447b37
Author: David Bokan <bokan@chromium.org>
Date: Fri Jan 12 19:29:09 2018

Fix rootScroller URL bar adjustment under root-layer-scrolls

position: fixed elements fixed to the bottom of the viewport require a
special adjustment on Android due to the URL bar. As the URL bar hides,
the viewport becomes taller; however, for performance reasons we can't
resize the Blink widget at 60fps. Since layers are positioned from the
top left, until Blink resizes the bottom-fixed layer will no longer be
at the bottom of the viewport. To account for this, CC adjusts
bottom-fixed layers by the URL bar offset. This adjustment is cleared
when the Blink widget is resized and committed.

Blink marks position-fixed containing layers that should apply this
adjustment using SetIsResizedByBrowserControls. This is marked on all
LayoutViews that have the global root-scroller as a descendant. This is
so that, if the global root-scroller is inside an iframe, fixed elements
in both the iframe and the parent frame will be adjusted.

Prior to this CL, PLC would mark each root layer's scroll layer
appropriately. However, IsFixedContainer is set from CLM on all child
layers. When the property tree is built, it's actually the scrolling
contents layer that fixed-layers will attach to so it too must be marked
as IsResizedByBrowserControls. This CL moves this logic to CLM and marks
the same layers as are marked for IsFixedContainer (but on the root
layer only).

Additionally, LayoutViews that have a root-scroller as a descendant
shouldn't clip since they're guaranteed to be viewport-filling - this
prevents clipping out content below as the URL bar is hidden. For the
non-RLS case this happens by marking the OverflowControlsHostLayer as
non-MasksToBounds. This CL extends this behavior to the root layer's
CLM when running with RLS.

Finally, as a small cleanup, I've removed the pointless indirection of
SetLayerIsContainerForFixedPositionLayers through ScrollingCoordinator
and made it directly settable on GraphicsLayer. This makes it consistent
with other similar properties.


Bug:  773362 
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I547f344c15fc0c25c48161e8eee1e8440960edcc
Reviewed-on: https://chromium-review.googlesource.com/854735
Reviewed-by: Steve Kobes <skobes@chromium.org>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#529016}
[modify] https://crrev.com/e1bfa83b72c16ce19270d8e5641aa2bc46447b37/third_party/WebKit/LayoutTests/FlagExpectations/root-layer-scrolls
[modify] https://crrev.com/e1bfa83b72c16ce19270d8e5641aa2bc46447b37/third_party/WebKit/Source/core/frame/VisualViewport.cpp
[modify] https://crrev.com/e1bfa83b72c16ce19270d8e5641aa2bc46447b37/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
[modify] https://crrev.com/e1bfa83b72c16ce19270d8e5641aa2bc46447b37/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
[modify] https://crrev.com/e1bfa83b72c16ce19270d8e5641aa2bc46447b37/third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.cpp
[modify] https://crrev.com/e1bfa83b72c16ce19270d8e5641aa2bc46447b37/third_party/WebKit/Source/core/paint/compositing/CompositedLayerMapping.cpp
[modify] https://crrev.com/e1bfa83b72c16ce19270d8e5641aa2bc46447b37/third_party/WebKit/Source/core/paint/compositing/PaintLayerCompositor.cpp
[modify] https://crrev.com/e1bfa83b72c16ce19270d8e5641aa2bc46447b37/third_party/WebKit/Source/core/paint/compositing/PaintLayerCompositor.h
[modify] https://crrev.com/e1bfa83b72c16ce19270d8e5641aa2bc46447b37/third_party/WebKit/Source/platform/graphics/GraphicsLayer.cpp
[modify] https://crrev.com/e1bfa83b72c16ce19270d8e5641aa2bc46447b37/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h