Set ComputedStyle on Node and use that in buildOwnLayout()

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

Index: third_party/WebKit/Source/core/dom/NodeComputedStyle.h
diff --git a/third_party/WebKit/Source/core/dom/NodeComputedStyle.h b/third_party/WebKit/Source/core/dom/NodeComputedStyle.h
index 4d7e9d6db263d9ab79aa80a8c2cc1f26f26cf6b5..07663500c0e3022a58e10055e2858cb4f2b7636b 100644
--- a/third_party/WebKit/Source/core/dom/NodeComputedStyle.h
+++ b/third_party/WebKit/Source/core/dom/NodeComputedStyle.h
@@ -58,6 +58,27 @@ inline ComputedStyle* Node::mutableComputedStyle() const
     return m_data.m_computedStyle;
 }
 
+inline void Node::setComputedStyle(PassRefPtr<ComputedStyle> computedStyle)
+{
+    if (hasRareData()) {

[sashab, 2016/07/06 04:22:02]

Is hasRareData() the check you want here? Maybe you want isElement().

Did you copy this code from somewhere or is this your own logic?

[nainar, 2016/07/06 04:51:53]

Yup. The ComputedStyle on Node can be stored in the following ways:

If the DataUnion is a NodeRareDataBase and has a LayoutObject - set the
ComputedStyle on that LayoutObject
If the DataUnion is an NodeRareDataBase (specifically an ElementRareData) - set
the ComputedStyle on that LayoutObject
If the DataUnion is a LayoutObject - set the ComputedStyle on that LayoutObject
If the DataUnion is a ComputedStyle - make it point to the new ComputedStyle
passed in. 

Bugs' had written up a draft of this code in his CL - however didn't land it as
it wasn't needed as part of that CL. I modified it a bit.

[sashab, 2016/07/06 05:10:40]

Could you re-write this as a single if-statement with 4 branches? Might be a
little easier to understand. Put what you've explained above in comments if you
can, in each branch. :)

+        if (hasLayoutObject()) {

[Bugs Nash, 2016/07/06 04:30:42]

this isn't necessary

[nainar, 2016/07/06 04:51:53]

Agreed in a screen-to-screen conversation that:

Quoting the design doc here: "If NodeRareDataBase exists, the ComputedStyle will
be stored within the LayoutObject, which is stored within the NodeRareDataBase
on the DataUnion. If there is no LayoutObject stored on NodeRareDataBase we
directly store the ComputedStyle on the NodeRareDataBase (specifically the
ElementRareData)."

+            m_data.m_rareData->layoutObject()->setStyleInternal(computedStyle);
+        } else {
+            NodeRareData* rareData = this->rareData();
+            DCHECK(rareData->isElementRareData());
+            static_cast<ElementRareData*>(rareData)->setComputedStyle(computedStyle);
+        }
+    } else {
+        if (hasLayoutObject()) {
+            m_data.m_layoutObject->setStyleInternal(computedStyle);
+        } else {
+            if (m_data.m_computedStyle)
+                m_data.m_computedStyle->deref();
+            m_data.m_computedStyle = computedStyle.leakRef();
+        }
+    }
+}
+
 inline const ComputedStyle* Node::parentComputedStyle() const
 {
     if (isSlotOrActiveInsertionPoint())