Revert "Promote BlinkGenPropertyTrees to experimental"

This reverts commit 00868f0800150009e4cd5575e2477c566817fc43.

Reason for revert: Due to animations fix being reverted, this needs to be reverted to prevent crashes for users with experimental web platform features enabled. See: http://crrev.com/621553.

Original change's description:
> Promote BlinkGenPropertyTrees to experimental
> 
> This is another [1] patch promoting BlinkGenPropertyTrees (BGPT) to
> experimental. BlinkGenPropertyTrees is an incremental step towards
> making compositing decisions after the paint lifecycle phase. The
> primary changes are to build property trees in blink and send a layer
> list to the compositor, rather than building property trees in cc from a
> layer tree.
> 
> This shifts time (e.g., we now run PaintArtifactCompositor and no longer
> run the cc property tree builder) and will likely change performance
> benchmarks.
> 
> [1] Previous attempts at enabling BGPT
> Demote BlinkGenPropertyTrees from experimental to test: https://crrev.com/616506
> Promote BGPT to experimental: https://crrev.com/614470
> Revert Promote BGPT to experimental: https://crrev.com/603710
> Promote BGPT to experimental: https://crrev.com/602150
> Revert Promote BGPT to experimental: https://crrev.com/601624
> Promote BGPT to experimental: https://crrev.com/601429
> 
> Bug: 836884
> Change-Id: I2251041af1d5c33407081f3888053a248eb33491
> Reviewed-on: https://chromium-review.googlesource.com/c/1403516
> Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
> Commit-Queue: Philip Rogers <pdr@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#621273}

TBR=pdr@chromium.org,chrishtr@chromium.org

Change-Id: Icde34c5a1d2d8ac148a34fcb6eebd2e489dbbaf8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 836884
Reviewed-on: https://chromium-review.googlesource.com/c/1405499
Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621669}
1 file changed