Refactoring markers.html to use async path for spellcheck

Rewrite spelling/markers.html to use asynchronous spellchecking.
Additionally, remove unnecessary code.

BUG=295722

Review URL: https://codereview.chromium.org/59143005

git-svn-id: svn://svn.chromium.org/blink/trunk@161435 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Refactoring inline_spelling_markers.html to use async path for spellcheck

This change mostly adapts inline_spelling_markers.html to use asynchronous
path for spellchecking which will be enabled by default.
To achieve this, shouldBecomeEqual helper has been used.

Additionally, make cross platform text expectation by dumping
spelling/grammar markers instead of whole tree which in terms
of spellchecking says nothing.

Enabling unified text checker and adjusting MockGrammarCheck.cpp
allow us to restore grammar checking in inline_spelling_markers.html.

Remove unnecessary new lines in div elements so position of markers
can be given from 0.

BUG=295722

Review URL: https://codereview.chromium.org/49613006

git-svn-id: svn://svn.chromium.org/blink/trunk@161436 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Web Animations CSS: Fix crash when transitioning background or mask properties

This patch ensures the first layer for background and mask declares that
their values are set. This has no visible effect on the way fill layers
work, this just ensures an assertion made by the Web Animations engine
about fill layer properties is correct.

The current animation implementation did not make use of the flags on a fill layer
that indicate whether a value was set or not and will be agnostic to this change.
In order to implement correct interpolation behaviour[1] for many fill layer
properties these flags need to be used.
The existing FillLayer implementation was not setting these flags correctly for
the initial values, this patch fixes that.

[1] http://www.w3.org/TR/css3-transitions/#animtype-repeatable-list

Fixes crashing tests:
virtual/web-animations-css/transitions/multiple-background-size-transitions.html
virtual/web-animations-css/transitions/shorthand-transitions.html

BUG=257591

Review URL: https://codereview.chromium.org/38573005

git-svn-id: svn://svn.chromium.org/blink/trunk@161438 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Adapt hidpi spelling tests to use async path for spellcheck

Apply changes from https://codereview.chromium.org/49613006/ to
inline-spelling-markers-hidpi.html and
editing/spelling/inline-spelling-markers-hidpi-composited.html.

BUG=295722

Review URL: https://codereview.chromium.org/57823002

git-svn-id: svn://svn.chromium.org/blink/trunk@161439 bbb929c8-8fbe-4397-9dbb-9b2b20218538