cc: Remove legacy update loop

Now that impl-side painting is always on, using_only_property_trees is
always true on the main thread, so the old update loop can be removed.

Because the old update loop is not on any more, several tiled layer unit
tests start failing due to prioritization and partial updates.  Since
tiled layer is on the way out, this CL just removes the whole unit test
file.

R=danakj,vmpstr
BUG=413479
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1188853002

Cr-Commit-Position: refs/heads/master@{#334877}

• cc/BUILD.gn[diff]
• cc/cc_tests.gyp[diff]
• cc/layers/layer.cc[diff]
• cc/layers/painted_scrollbar_layer.cc[diff]
• cc/layers/tiled_layer_unittest.cc[Deleted - diff]
• cc/trees/layer_tree_host.cc[diff]
• cc/trees/layer_tree_host.h[diff]