Enable "RestrictedWebkitAppearance" flag as "experimental".

* insert_paragraph_separator_command_test.cc
  <colgroup>'s actual appearance will be 'none', and it has no height.

* external/wpt/css/css-lists/list-and-margin-collapse-003.html and -004.html
  <div> can't have 'checkbox' appearance any longer, and we couldn't find other
  ways to reproduce the original issue.  So we remove the tests.

* fast/css/invalid-appearance.html
  Removed.  It was made to check deprecation messages.

* fast/css/square-button-appearance.html
  Removed. -webkit-appearance:square-button doesn't work for arbitrary elements
  any longer, and its appearance is tested in input[type=color] tests.

* fast/forms/file/file-style-inheritance.html
  -webkit-appearance:square-button doesn't work for ::-webkit-file-upload-button
  any longer. -webkit-appearnace:none works well in the test.

* fast/forms/range/thumbslider-no-parent-slider.html
  -webkit-appearance:slider-thumb-* don't work in this case any longer. Its
  pixel result has nothing. This CL converts the test to a reference test.

* scrollbars/custom-scrollbar-appearance-property.html
  -webkit-appearance:searchfield-cancel-button doesn't work for
  ::-webkit-scrollbar* any longer, and pixel result of this test would be
  changed.  This CL converts the test to a testharness.js test.

* fast/css/invalid-appearance-progress-bar-meter-expected.txt
* fast/forms/datalist/slider-appearance-with-ticks-crash-expected.txt
* fast/forms/range/slider-appearance-crash-expected.txt
* fast/forms/range/thumbslider-crash-expected.txt
* fast/text/whitespace/pre-block-normal-inline-crash-2-expected.txt
* paint/invalidation/selection/multiple-body-remove-selection-crash-expected.txt
* paint/theme/anonymous-element-menulist-painting-expected.txt
  Remove deprecation messages.

Bug: 981720
Change-Id: I91068c8265cdfc682a06b1b4588b04ea30a318d0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1727654
Reviewed-by: Yoshifumi Inoue <[email protected]>
Commit-Queue: Kent Tamura <[email protected]>
Cr-Commit-Position: refs/heads/master@{#684247}

Author: tkent-google