Don't bother layout until first navigation is done.

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

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index ea7f805bbf5f360876100e88fef50b44a8d69660..dbda6a31b173151b89a294bd4ea5809212ea5668 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -1736,15 +1736,20 @@ void Document::updateLayoutTree(StyleRecalcChange change)
     if (view()->shouldThrottleRendering())
         return;
 
-    if (change != Force && !needsLayoutTreeUpdate()) {
-        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);
+    if (change != Force) {
+        if (isInitialEmptyDocument())
+            return;
+
+        if (!needsLayoutTreeUpdate()) {
+            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;
         }
-        return;
     }
 
     if (inStyleRecalc())
@@ -2800,7 +2805,7 @@ void Document::dispatchUnloadEvents()
         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();
@@ -5467,6 +5472,11 @@ 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::setContextFeatures(ContextFeatures& features)
 {
     m_contextFeatures = PassRefPtrWillBeRawPtr<ContextFeatures>(features);