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This implements logic to evict from SW image decode cache
in cc, based on skia unique image id. We add a auxiliary
map of image id and key, and use it for optimizing search
and access. New api's to handle cache addition and deletion
is also added.

BUG=734982
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

patch from issue 2951093002 at patchset 80001 (http://crrev.com/2951093002#ps80001)

Change-Id: Iab533d140802a0308bf2143765708257a465bd31
Reviewed-on: https://chromium-review.googlesource.com/571459Reviewed-by: Eric Karl <ericrk@chromium.org>
Reviewed-by: Vladimir Levin <vmpstr@chromium.org>
Reviewed-by: Sohan Jyoti Ghosh <sohan.jyoti@huawei.com>
Commit-Queue: Sohan Jyoti Ghosh <sohan.jyoti@huawei.com>
Cr-Commit-Position: refs/heads/master@{#488829}