Don't bother layout until first navigation is done.

third_party/WebKit/Source/core/editing/FrameSelection.cpp

 /*
  * Copyright (C) 2004, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 891 matching lines @@
 {
     bool activeAndFocused = isFocusedAndActive();
     RefPtrWillBeRawPtr<Document> document = m_frame->document();
 
     // Trigger style invalidation from the focused element. Even though
     // the focused element hasn't changed, the evaluation of focus pseudo
     // selectors are dependent on whether the frame is focused and active.
     if (Element* element = document->focusedElement())
         element->focusStateChanged();
 
-    document->updateLayoutTreeIfNeeded();
+    if (!document->isInitialEmptyDocument())

[tkent, 2016/01/21 02:19:32]

Can you move isInitialEmptyDocument() check to Document::updateLayoutTree(),
FrameView::layout(), or something deeper place?

[kouhei (in TOK), 2016/02/18 03:50:49]

Done.

+        document->updateLayoutTreeIfNeeded();
 
     // Because LayoutObject::selectionBackgroundColor() and
     // LayoutObject::selectionForegroundColor() check if the frame is active,
     // we have to update places those colors were painted.
     if (LayoutView* view = document->layoutView())
         view->invalidatePaintForSelection();
 
     // Caret appears in the active frame.
     if (activeAndFocused)
         setSelectionFromNone();
@@ skipping 482 matching lines @@
 
 void showTree(const blink::FrameSelection* sel)
 {
     if (sel)
         sel->showTreeForThis();
     else
         fprintf(stderr, "Cannot showTree for (nil) FrameSelection.\n");
 }
 
 #endif