Don't setStyle the RenderView every style recalc

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 1642 matching lines @@
     // and then trigger a full document recalc. We also need to clear it here since the
     // call to styleForElement on the body above can cache bad values for rem units if the
     // documentElement's style was dirty. We could keep track of which elements depend on
     // rem units like we do for viewport styles, but we assume root font size changes are
     // rare and just invalidate the cache for now.
     if (styleEngine()->usesRemUnits() && (documentElement()->needsAttach() || documentElement()->computedStyle()->fontSize() != documentElementStyle->fontSize())) {
         ensureStyleResolver().invalidateMatchedPropertiesCache();
         documentElement()->setNeedsStyleRecalc(SubtreeStyleChange);
     }
 
+    EOverflow overflowX = OAUTO;
+    EOverflow overflowY = OAUTO;
+    float columnGap = 0;
+    if (overflowStyle) {
+        overflowX = overflowStyle->overflowX();
+        overflowY = overflowStyle->overflowY();
+        // Visible overflow on the viewport is meaningless, and the spec says to treat it as 'auto':
+        if (overflowX == OVISIBLE)
+            overflowX = OAUTO;
+        if (overflowY == OVISIBLE)
+            overflowY = OAUTO;
+        // Column-gap is (ab)used by the current paged overflow implementation (in lack of other
+        // ways to specify gaps between pages), so we have to propagate it too.
+        columnGap = overflowStyle->columnGap();
+    }
+
     RefPtr<RenderStyle> documentStyle = renderView()->style();
     if (documentStyle->writingMode() != rootWritingMode
         || documentStyle->direction() != rootDirection
-        || (overflowStyle && (documentStyle->overflowX() != overflowStyle->overflowX() || documentStyle->overflowY() != overflowStyle->overflowY()))) {
+        || documentStyle->overflowX() != overflowX
+        || documentStyle->overflowY() != overflowY
+        || documentStyle->columnGap() != columnGap) {
         RefPtr<RenderStyle> newStyle = RenderStyle::clone(documentStyle.get());
         newStyle->setWritingMode(rootWritingMode);
         newStyle->setDirection(rootDirection);
-        EOverflow overflowX = OAUTO;
-        EOverflow overflowY = OAUTO;
-        if (overflowStyle) {
-            overflowX = overflowStyle->overflowX();
-            overflowY = overflowStyle->overflowY();
-            // Visible overflow on the viewport is meaningless, and the spec says to treat it as 'auto':
-            if (overflowX == OVISIBLE)
-                overflowX = OAUTO;
-            if (overflowY == OVISIBLE)
-                overflowY = OAUTO;
-
-            // Column-gap is (ab)used by the current paged overflow implementation (in lack of other
-            // ways to specify gaps between pages), so we have to propagate it too.
-            newStyle->setColumnGap(overflowStyle->columnGap());
-        }
+        newStyle->setColumnGap(columnGap);
         newStyle->setOverflowX(overflowX);
         newStyle->setOverflowY(overflowY);
         renderView()->setStyle(newStyle);
         setupFontBuilder(newStyle.get());
     }
 
     if (body) {
         if (RenderStyle* style = body->renderStyle()) {
             if (style->direction() != rootDirection || style->writingMode() != rootWritingMode)
                 body->setNeedsStyleRecalc(SubtreeStyleChange);
@@ skipping 3739 matching lines @@
 void Document::defaultEventHandler(Event* event)
 {
     if (frame() && frame()->remotePlatformLayer()) {
         frame()->chromeClient().forwardInputEvent(this, event);
         return;
     }
     Node::defaultEventHandler(event);
 }
 
 } // namespace WebCore