Change text document to no-quirks mode

Quirks mode layout is slower, so change to no-quirks.

Note that this goes against the spec [1], which mandates quirks
mode for text documents. An issue [2] has been raised to change
that, but in the meantime, this seems like a very low (compat)
risk change. For now, however, the WPT test will not be changed,
and a broken expectation will be committed.

[1] https://html.spec.whatwg.org/multipage/browsing-the-web.html#read-text
[2] https://github.com/whatwg/html/issues/5939

Bug: 1131185
Change-Id: If7ac8cbe8b4ec277f2cb288d120698b9bacf773c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2425109
Commit-Queue: Mason Freed <masonfreed@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Auto-Submit: Mason Freed <masonfreed@chromium.org>
Cr-Commit-Position: refs/heads/master@{#810357}

third_party/blink/renderer/core/html/text_document.cc

@@ -32,7 +32,7 @@ namespace blink {
 
 TextDocument::TextDocument(const DocumentInit& initializer)
     : HTMLDocument(initializer) {
-  SetCompatibilityMode(kQuirksMode);
+  SetCompatibilityMode(kNoQuirksMode);
   LockCompatibilityMode();
 }
 

third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/read-text/load-text-plain-expected.txt

+This is a testharness.js-based test.
+FAIL Checking document metadata for text file assert_equals: expected "BackCompat" but got "CSS1Compat"
+PASS Checking DOM for text file
+PASS Checking contents for text file
+Harness: the test ran to completion.
+