Revert "Hold pre-decoded images until use or 250ms rather than 2 frames"

This reverts commit 520ce5d7136360877309b68ab8b43a7d13c84d82.

Reason for revert: breaking blink_perf.image_decoder/* tests

BUG:chromium:874810

Original change's description:
> Hold pre-decoded images until use or 250ms rather than 2 frames
> 
> We currently unlock pre-decoded images after 2 frames of any type. This
> doesn't always give callers a chance to use their images (if main thread
> is a bit backed up). Instead we should wait for the caller to actually
> use the image. Additionally, we drop images after 250ms to prevent
> excessive growth if a user fails to use images in a timely manner.
> 
> See the linked bug for example traces which show the benefits.
> 
> R=​khushalsagar
> 
> Bug: 869491
> Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
> Change-Id: Icd94709aad5c076b1ba295495eaab24dc893ebdb
> Reviewed-on: https://chromium-review.googlesource.com/1159203
> Commit-Queue: Eric Karl <ericrk@chromium.org>
> Reviewed-by: Khushal <khushalsagar@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#583171}

TBR=khushalsagar@chromium.org,ericrk@chromium.org

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

Bug: 869491
Change-Id: Ia80ab26563bf1ccc0556d5638a483337acee972d
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Reviewed-on: https://chromium-review.googlesource.com/1178841
Reviewed-by: Ned Nguyen <nednguyen@google.com>
Commit-Queue: Ned Nguyen <nednguyen@google.com>
Cr-Commit-Position: refs/heads/master@{#583855}

• cc/tiles/decoded_image_tracker.cc[diff]
• cc/tiles/decoded_image_tracker.h[diff]
• cc/tiles/decoded_image_tracker_unittest.cc[diff]
• cc/tiles/tile_manager.cc[diff]
• cc/tiles/tile_manager_unittest.cc[diff]
• cc/trees/layer_tree_host_impl.cc[diff]