Revert "[IO] Only compute intersection observations if any property tree state has changed, and only for full-frame updates."

This reverts commit cdea59c0db145f8e85ea00e9f6d31642929e2397.

Reason for revert: Suspect of causing flakes in SitePerProcessBrowserTest.ChildFrameCrashMetrics_ScrolledIntoView

Original change's description:
> [IO] Only compute intersection observations if any property tree state has changed, and only for full-frame updates.
> 
> This avoids re-computing intersection observations when nothing has changed.
> 
> It is correct for IOv1 and also IOv2. It is correct for IOv2 because at present
> IOv2 and hit testing do not depend on paint output.
> 
> Bug: 831762
> Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
> Change-Id: I196ca3a64e26d2227bc8cbb6b73ea81c1adbb4b2
> Reviewed-on: https://chromium-review.googlesource.com/1134348
> Reviewed-by: Stefan Zager <szager@chromium.org>
> Reviewed-by: vmpstr <vmpstr@chromium.org>
> Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#574755}

TBR=szager@chromium.org,vmpstr@chromium.org,chrishtr@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 831762, 863946
Change-Id: I30ab56ebce4cb3e677623f7663eb2795b0201274
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Reviewed-on: https://chromium-review.googlesource.com/1138894
Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575473}
6 files changed