Set ComputedStyle on Node and use that in buildOwnLayout()

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

Index: third_party/WebKit/Source/core/dom/Element.cpp
diff --git a/third_party/WebKit/Source/core/dom/Element.cpp b/third_party/WebKit/Source/core/dom/Element.cpp
index 190d1908070ca33a5920d6240e84c09f3b46732a..abb5e45216633de1f2d3efdb88f616a512911781 100644
--- a/third_party/WebKit/Source/core/dom/Element.cpp
+++ b/third_party/WebKit/Source/core/dom/Element.cpp
@@ -567,7 +567,7 @@ void Element::nativeApplyScroll(ScrollState& scrollState)
     // page removes the default applyScroll (ViewportScrollCallback).
     if (document().effectiveRootScroller() == this)
         boxToScroll = document().layoutView();
-    else if (layoutObject())
+    else if (hasLayoutObject())
         boxToScroll = toLayoutBox(layoutObject());
 
     if (!boxToScroll)
@@ -1769,13 +1769,8 @@ StyleRecalcChange Element::recalcOwnStyle(StyleRecalcChange change)
     }
 
     if (localChange == Reattach) {
-        AttachContext reattachContext;
-        reattachContext.resolvedStyle = newStyle.get();
-        bool layoutObjectWillChange = needsAttach() || layoutObject();
-        reattach(reattachContext);
-        if (layoutObjectWillChange || layoutObject())
-            return Reattach;
-        return ReattachNoLayoutObject;
+        setComputedStyle(newStyle);
+        return buildOwnLayout();

[sashab, 2016/07/04 07:57:12]

A suggestion that might make this a little easier to understand/track bugs
for/test:

1. Land a mechanical change patch that just calls buildOwnLayout(newStyle) here,
with a TODO to say //TODO(nainar): Remove the style parameter from this function
2. Make a separate patch that splits buildOwnLayout() into the two functions, an
actual behavioural change

From my experience it's a ton easier to land mechanical changes - they are less
likely to break things, get reverted, etc. Also if anything is wrong with them
you know the patch is wrong. If we can move all the significant changes for this
into a tiny change at the end it'll be much easier to see and understand. :)

[nainar, 2016/07/05 00:26:55]

In progress update: Made a new CL with the mechanical change and the TODO as you
suggested here: https://codereview.chromium.org/2118393002

     }
 
     DCHECK(oldStyle);
@@ -1814,6 +1809,17 @@ StyleRecalcChange Element::recalcOwnStyle(StyleRecalcChange change)
     return localChange;
 }
 
+StyleRecalcChange Element::buildOwnLayout()
+{
+    AttachContext reattachContext;
+    reattachContext.resolvedStyle = mutableComputedStyle();
+    bool layoutObjectWillChange = needsAttach() || hasLayoutObject();
+    reattach(reattachContext);
+    if (layoutObjectWillChange || hasLayoutObject())
+        return Reattach;
+    return ReattachNoLayoutObject;
+}
+
 void Element::updateCallbackSelectors(const ComputedStyle* oldStyle, const ComputedStyle* newStyle)
 {
     Vector<String> emptyVector;