Remove RequireCSSExtensionForFile runtime enabled flag.

The feature has long since been stable (since M64) and doesn't seem
to be a need for this flag.

BUG=788936

Change-Id: I666390b869289c328acb4a2daa5bf4154e1702c0
Reviewed-on: https://chromium-review.googlesource.com/c/1324143
Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Camille Lamy <clamy@chromium.org>
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607329}
StyleSheetContents* CSSStyleSheetResource::CreateParsedStyleSheetFromCache(
    const CSSParserContext* context) {
  if (!parsed_style_sheet_cache_)
    return nullptr;
  if (parsed_style_sheet_cache_->HasFailedOrCanceledSubresources()) {
    SetParsedStyleSheetCache(nullptr);
    return nullptr;
  }

  DCHECK(parsed_style_sheet_cache_->IsCacheableForResource());
  DCHECK(parsed_style_sheet_cache_->IsReferencedFromResource());

  if (*parsed_style_sheet_cache_->ParserContext() != *context)
    return nullptr;

  DCHECK(!parsed_style_sheet_cache_->IsLoading());

  if (RuntimeEnabledFeatures::CacheStyleSheetWithMediaQueriesEnabled() &&
      parsed_style_sheet_cache_->HasMediaQueries()) {
    return parsed_style_sheet_cache_->Copy();
  }

  return parsed_style_sheet_cache_;
}

StyleSheetContents* CSSStyleSheetResource::CreateParsedStyleSheetFromCache(
    const CSSParserContext* context) {
  if (!parsed_style_sheet_cache_)
    return nullptr;
  if (parsed_style_sheet_cache_->HasFailedOrCanceledSubresources()) {
    SetParsedStyleSheetCache(nullptr);
    return nullptr;
  }

  DCHECK(parsed_style_sheet_cache_->IsCacheableForResource());
  DCHECK(parsed_style_sheet_cache_->IsReferencedFromResource());

  if (*parsed_style_sheet_cache_->ParserContext() != *context)
    return nullptr;

  DCHECK(!parsed_style_sheet_cache_->IsLoading());

  if (RuntimeEnabledFeatures::CacheStyleSheetWithMediaQueriesEnabled() &&
      parsed_style_sheet_cache_->HasMediaQueries()) {
    return parsed_style_sheet_cache_->Copy();
  }

  return parsed_style_sheet_cache_;
}
