Revert "Suspend SVG image animations when the page is hidden"

This reverts commit b56e2510d08c0a8fd0be69ad29a2558c6ce63523.

Reason for revert: Test flaky on cast_shell_linux

Original change's description:
> Suspend SVG image animations when the page is hidden
> 
> Check Document::hidden() in LayoutObject::WillRenderImage,
> thus pausing animations on pages that are not visible.
> To resume animations, we may need to explicitly resume the
> timeline, so a hook is added in Page::SetVisibilityState to
> allow calling StartAnimation() on the relevant SVGImages.
> 
> Bug: 856082
> Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
> Change-Id: I4a0b008730ec3e6c2af26e15d52eebb26020ad32
> Reviewed-on: https://chromium-review.googlesource.com/1115130
> Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
> Commit-Queue: Fredrik Söderquist <fs@opera.com>
> Cr-Commit-Position: refs/heads/master@{#571543}

TBR=fs@opera.com,chrishtr@chromium.org

Change-Id: I53a07f59bf48095c21ccf6eb357162786012ad1c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 856082
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/1120976
Reviewed-by: Fredrik Söderquist <fs@opera.com>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#571587}
7 files changed