Don't bother layout until first navigation is done.

third_party/WebKit/Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 1729 matching lines @@
         if (lifecycle().state() < DocumentLifecycle::StyleClean) {
             // needsLayoutTreeUpdate may change to false without any actual layout tree update.
             // For example, needsAnimationTimingUpdate may change to false when time elapses.
             // Advance lifecycle to StyleClean because style is actually clean now.
             lifecycle().advanceTo(DocumentLifecycle::InStyleRecalc);
             lifecycle().advanceTo(DocumentLifecycle::StyleClean);
         }
         return;
     }
 
+    if (m_frame && m_frame->isMainFrame() && isInitialEmptyDocument())
+        return;
+
     if (inStyleRecalc())
         return;
 
     // Entering here from inside layout or paint would be catastrophic since recalcStyle can
     // tear down the layout tree or (unfortunately) run script. Kill the whole layoutObject if
     // someone managed to get into here from inside layout or paint.
     RELEASE_ASSERT(!view()->isInPerformLayout());
     RELEASE_ASSERT(!view()->isPainting());
 
     // Script can run below in WidgetUpdates, so protect the LocalFrame.
@@ skipping 232 matching lines @@
 }
 
 // FIXME: This is a bad idea and needs to be removed eventually.
 // Other browsers load stylesheets before they continue parsing the web page.
 // Since we don't, we can run JavaScript code that needs answers before the
 // stylesheets are loaded. Doing a layout ignoring the pending stylesheets
 // lets us get reasonable answers. The long term solution to this problem is
 // to instead suspend JavaScript execution.
 void Document::updateLayoutTreeIgnorePendingStylesheets()
 {
+    // TODO(kouhei): We need forced layout at this point. Bail out from skip layout tree path.
+    markNonInitialEmptyDocument();
+
     StyleEngine::IgnoringPendingStylesheet ignoring(styleEngine());
 
     if (styleEngine().hasPendingSheets()) {
         // FIXME: We are willing to attempt to suppress painting with outdated style info only once.
         // Our assumption is that it would be dangerous to try to stop it a second time, after page
         // content has already been loaded and displayed with accurate style information. (Our
         // suppression involves blanking the whole page at the moment. If it were more refined, we
         // might be able to do something better.) It's worth noting though that this entire method
         // is a hack, since what we really want to do is suspend JS instead of doing a layout with
         // inaccurate information.
@@ skipping 784 matching lines @@
                 m_frame->localDOMWindow()->dispatchEvent(unloadEvent, m_frame->document());
             }
         }
         m_loadEventProgress = UnloadEventHandled;
     }
 
     if (!m_frame)
         return;
 
     // Don't remove event listeners from a transitional empty document (see https://bugs.webkit.org/show_bug.cgi?id=28716 for more information).
-    bool keepEventListeners = m_frame->loader().stateMachine()->isDisplayingInitialEmptyDocument() && m_frame->loader().provisionalDocumentLoader()
+    bool keepEventListeners = isInitialEmptyDocument() && m_frame->loader().provisionalDocumentLoader()
         && isSecureTransitionTo(m_frame->loader().provisionalDocumentLoader()->url());
     if (!keepEventListeners)
         removeAllEventListenersRecursively();
 }
 
 Document::PageDismissalType Document::pageDismissalEventBeingDispatched() const
 {
     if (m_loadEventProgress == BeforeUnloadEventInProgress)
         return BeforeUnloadDismissal;
     if (m_loadEventProgress == PageHideInProgress)
@@ skipping 2686 matching lines @@
 bool Document::threadedParsingEnabledForTesting()
 {
     return s_threadedParsingEnabledForTesting;
 }
 
 bool Document::hasActiveParser()
 {
     return m_activeParserCount || (m_parser && m_parser->processingData());
 }
 
+bool Document::isInitialEmptyDocument() const
+{
+    return m_frame && m_frame->loader().stateMachine()->isDisplayingInitialEmptyDocument();
+}
+
+void Document::markNonInitialEmptyDocument()
+{
+    if (!m_frame)
+        return;
+    auto stateMachine = m_frame->loader().stateMachine();
+    if (stateMachine->isDisplayingInitialEmptyDocument())
+        stateMachine->advanceTo(FrameLoaderStateMachine::CommittedFirstRealLoad);
+}
+
 void Document::setContextFeatures(ContextFeatures& features)
 {
     m_contextFeatures = PassRefPtrWillBeRawPtr<ContextFeatures>(features);
 }
 
 static LayoutObject* nearestCommonHoverAncestor(LayoutObject* obj1, LayoutObject* obj2)
 {
     if (!obj1 || !obj2)
         return 0;
 
@@ skipping 471 matching lines @@
 #ifndef NDEBUG
 using namespace blink;
 void showLiveDocumentInstances()
 {
     Document::WeakDocumentSet& set = Document::liveDocumentSet();
     fprintf(stderr, "There are %u documents currently alive:\n", set.size());
     for (Document* document : set)
         fprintf(stderr, "- Document %p URL: %s\n", document, document->url().string().utf8().data());
 }
 #endif