Convert fast/repaint/background-scaling.html to a reftest

Originally the test expects full repaint of the viewport on page scale
changes. However, the repaint is unnecessary because we handle page
scale in the compositor. My later change will optimize this.

Convert it to a reftest to ensure the visual result is correct.

BUG=258219

Review URL: https://codereview.chromium.org/267333008

git-svn-id: svn://svn.chromium.org/blink/trunk@173658 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add defensive code for now to RenderLayerRepainter to prevent squashing crashes
when removing certain kinds of layers.

BUG=370410

Review URL: https://codereview.chromium.org/270903002

git-svn-id: svn://svn.chromium.org/blink/trunk@173659 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Always use AwesomeResampling for lazy decoded images.

We don't know the real destination scale of lazy decoded images
and should not be making filter choices based on the
transformation matrix here.

Instead use AwesomeResampling for all lazy decoded images and
leaves it up to skia to decided if a more efficient filter can
be used at rasterization time.

BUG=368078

Review URL: https://codereview.chromium.org/262263003

git-svn-id: svn://svn.chromium.org/blink/trunk@173660 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Force composite compositing/ tests

BUG=361729,371111

Review URL: https://codereview.chromium.org/271553004

git-svn-id: svn://svn.chromium.org/blink/trunk@173661 bbb929c8-8fbe-4397-9dbb-9b2b20218538