Make HTML Imports deprecation message respect origin trials

Prior to this CL, the HTML Imports deprecation message would only
be shown if HTML Imports was enabled directly by a command line
flag. It would not show if the page being visited was participating
in the Web Components v0 origin trial, and enabled the feature
that way.

Bug: 911943
Change-Id: I8884ea755fdcdd69e2af57c6f131eed83f76b4f0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1876799
Commit-Queue: Mason Freed <masonfreed@chromium.org>
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Auto-Submit: Mason Freed <masonfreed@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#708810}

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

@@ -69,7 +69,7 @@ void HTMLLinkElement::ParseAttribute(
   if (name == html_names::kRelAttr) {
     rel_attribute_ = LinkRelAttribute(value);
     if (rel_attribute_.IsImport() &&
-        RuntimeEnabledFeatures::HTMLImportsEnabledByRuntimeFlag()) {
+        RuntimeEnabledFeatures::HTMLImportsEnabled(&GetDocument())) {
       Deprecation::CountDeprecation(&GetDocument(), WebFeature::kHTMLImports);
     }
     rel_list_->DidUpdateAttributeValue(params.old_value, value);

third_party/blink/web_tests/virtual/origin-trials-runtimeflags-disabled/http/tests/origin_trials/webexposed/webcomponentsv0-usecounter-htmlimports-expected.txt

-This is a testharness.js-based test.
-FAIL Comfirm HTMLImportsOnReverseOriginTrials counter assert_true: expected true got false
-Harness: the test ran to completion.
-