Made ElementRareData store ComputedStyle on LayoutObject if possible.

third_party/WebKit/Source/core/dom/ElementRareData.h

 /*
  * Copyright (C) 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2008 David Smith <catfish.man@gmail.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 73 matching lines @@
     ElementShadow& ensureShadow()
     {
         if (!m_shadow)
             m_shadow = ElementShadow::create();
         return *m_shadow;
     }
 
     NamedNodeMap* attributeMap() const { return m_attributeMap.get(); }
     void setAttributeMap(NamedNodeMap* attributeMap) { m_attributeMap = attributeMap; }
 
-    ComputedStyle* computedStyle() const { return m_computedStyle.get(); }
-    void setComputedStyle(PassRefPtr<ComputedStyle> computedStyle) { m_computedStyle = computedStyle; }
+    ComputedStyle* computedStyle() const
+    {

[Timothy Loh, 2016/09/07 04:56:07]

Maybe DCHECK(!(layoutObject() && m_computedStyle)) here

[Bugs Nash, 2016/09/13 21:46:55]

Done.

+        if (layoutObject())
+            return layoutObject()->mutableStyle();
+        return m_computedStyle.get();
+    }
+    void setComputedStyle(PassRefPtr<ComputedStyle> computedStyle)
+    {
+        if (layoutObject())
+            layoutObject()->setStyleInternal(computedStyle);
+        else
+            m_computedStyle = computedStyle;
+    }
     void clearComputedStyle() { m_computedStyle = nullptr; }

[Timothy Loh, 2016/09/07 04:56:07]

OK for now but at some point we should work out if we actually need this because
it's a bit weird. Please add a comment because otherwise it looks like it's just
doing the wrong thing.

[Bugs Nash, 2016/09/13 21:46:55]

As per offline conversation the usage of this method only works when there is no
LayoutObject. I did a dry run with all 3 call sites only calling this method if
there is no LayoutObject and it passed. I the ntried removing the check for a
LayoutObject in each of the 3 call sites 1 at at time and the bots failed for
all 3 (see https://codereview.chromium.org/2318973003). Therefore I think the
best solution is to keep the functionality in this patch and change the name of
this method to clearComputedStyleIfNoLayoutObject to make it clear that this
will not clear the ComputedStyle on the LayoutObject. I've also added a DCHECK
that there isn't simultaneously a LayoutObject and a separate ComputedStyle as
this may lead to unexpected behavior.

 
     ClassList* classList() const { return m_classList.get(); }
     void setClassList(ClassList* classList) { m_classList = classList; }
     void clearClassListValueForQuirksMode()
     {
         if (!m_classList)
             return;
         m_classList->clearValueForQuirksMode();
     }
 
@@ skipping 140 matching lines @@
 inline CompositorProxiedPropertySet& ElementRareData::ensureCompositorProxiedPropertySet()
 {
     if (!m_proxiedProperties)
         m_proxiedProperties = CompositorProxiedPropertySet::create();
     return *m_proxiedProperties;
 }
 
 } // namespace blink
 
 #endif // ElementRareData_h