Style recalc root is updated on element insertion.

No need to set a recalc root initially.

Change-Id: I27b0c5cd6bb0f0b50119e85b3a17b63a5619b3a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1837793Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702517}

third_party/blink/renderer/core/css/style_engine.cc

@@ -96,11 +96,8 @@ StyleEngine::StyleEngine(Document& document)
     viewport_resolver_ = MakeGarbageCollected<ViewportStyleResolver>(document);
   if (IsMaster())
     global_rule_set_ = MakeGarbageCollected<CSSGlobalRuleSet>();
-  // Document is initially style dirty.
-  style_recalc_root_.Update(nullptr, &document);
-  if (auto* settings = GetDocument().GetSettings()) {
+  if (auto* settings = GetDocument().GetSettings())
     preferred_color_scheme_ = settings->GetPreferredColorScheme();
-  }
 }
 
 StyleEngine::~StyleEngine() = default;