cc: Consolidate calls to the root scroll dalegate UpdateRootLayerState.
cc: Consolidate calls to the root scroll dalegate UpdateRootLayerState.

There's 2 different ways we call this function. Sometimes we call it
directly, and pass it the TotalScrollOffset.

Sometimes we call LayerTreeImpl::UpdateRootScrollOffsetDelegate() and
it computes the equivalent of TotalScrollOffset.

This merges them to all just call UpdateRootScrollOffsetDelegate() and
make that function use TotalScrollOffset().

R=boliu, jdduke
BUG=522658
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1315373006

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#348240}

Chilledheart/chromium,Chilledheart/chromium,Chilledheart/chromium,axinging/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,Chilledheart/chromium,Chilledheart/chromium