<rp> element should be display:none

This patch changes UA style sheet to make <rp> element has "display:none"
to follow the spec[1].

This patch improves pass rate of Element#innerTex spec conformance test
to 79 failures to 78 failures.

[1] https://html.spec.whatwg.org/multipage/rendering.html#non-replaced-elements

Bug: 859416
Change-Id: Ib5f41659d6ff056023dd24946e7c82cc388fba0e
Reviewed-on: https://chromium-review.googlesource.com/1122019Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571855}

third_party/WebKit/LayoutTests/external/wpt/html/dom/elements/the-innertext-idl-attribute/getter-expected.txt

 This is a testharness.js-based test.
-Found 213 tests; 134 PASS, 79 FAIL, 0 TIMEOUT, 0 NOTRUN.
+Found 213 tests; 135 PASS, 78 FAIL, 0 TIMEOUT, 0 NOTRUN.
 PASS Simplest possible test ("<div>abc")
 PASS Leading whitespace removed ("<div> abc")
 PASS Trailing whitespace removed ("<div>abc ")
@@ -202,7 +202,7 @@ PASS innerText not supported on SVG elements ("<svg>abc")
 PASS innerText not supported on MathML elements ("<math>abc")
 PASS <rt> and no <rp> ("<div><ruby>abc<rt>def</rt></ruby>")
 PASS <rp> ("<div><ruby>abc<rp>(</rp><rt>def</rt><rp>)</rp></ruby>")
-FAIL Lone <rp> ("<div><rp>abc</rp>") assert_equals: expected "" but got "abc"
+PASS Lone <rp> ("<div><rp>abc</rp>")
 PASS visibility:hidden <rp> ("<div><rp style='visibility:hidden'>abc</rp>")
 PASS display:block <rp> ("<div><rp style='display:block'>abc</rp>def")
 PASS display:block <rp> with whitespace ("<div><rp style='display:block'> abc </rp>def")

third_party/blink/renderer/core/css/html.css

@@ -1053,7 +1053,7 @@ ruby > rt {
     text-align: start;
 }
 
-ruby > rp {
+rp {
     display: none;
 }