Remove the forced layout in getComputedStyle for elements in Shadow DOM

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 2e5102eb0ff09212e3e4c0f555caa6deed66b926..e776d069457751020fc33a785280746b7bcec18b 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -1902,6 +1902,16 @@ void Document::notifyLayoutTreeOfSubtreeChanges()
     m_lifecycle.advanceTo(DocumentLifecycle::LayoutSubtreeChangeClean);
 }
 
+static bool nodeMayNeedStyleRecalc(const ContainerNode& node)

[rune, 2016/02/01 09:24:23]

Should we now use anonymous namespace instead of static functions? I couldn't
find anything about it in the Blink coding standard or in "C++11 use in
Chromium".

+{
+    return node.needsStyleRecalc() || node.needsStyleInvalidation() || node.needsAdjacentStyleRecalc();
+}
+
+static bool nodeMayNeedStyleRecalc(const ContainerNode* node)
+{
+    return node && nodeMayNeedStyleRecalc(*node);
+}
+
 void Document::updateLayoutTreeForNodeIfNeeded(Node* node)
 {
     ASSERT(node);
@@ -1915,8 +1925,14 @@ void Document::updateLayoutTreeForNodeIfNeeded(Node* node)
     bool needsRecalc = needsFullLayoutTreeUpdate() || node->needsStyleRecalc() || node->needsStyleInvalidation();
 
     if (!needsRecalc) {
-        for (const ContainerNode* ancestor = LayoutTreeBuilderTraversal::parent(*node); ancestor && !needsRecalc; ancestor = LayoutTreeBuilderTraversal::parent(*ancestor))
-            needsRecalc = ancestor->needsStyleRecalc() || ancestor->needsStyleInvalidation() || ancestor->needsAdjacentStyleRecalc();
+        LayoutTreeBuilderTraversal::ParentDetails parentDetails;
+        for (const ContainerNode* ancestor = LayoutTreeBuilderTraversal::parent(*node, &parentDetails); ancestor && !needsRecalc; ancestor = LayoutTreeBuilderTraversal::parent(*ancestor, &parentDetails)) {
+            needsRecalc = nodeMayNeedStyleRecalc(*ancestor) || nodeMayNeedStyleRecalc(parentDetails.shadowRoot());
+            parentDetails.reset();
+        }
+        // We may have bailed out of the loop because there's no ancestor in the
+        // composed tree, but we still need to check the shadow root.
+        needsRecalc = needsRecalc || nodeMayNeedStyleRecalc(parentDetails.shadowRoot());

[rune, 2016/02/01 09:24:23]

How could that happen? Won't every shadow root have a shadow host parent so that
the when we record a shadow root, the ancestor will be the shadow host?

     }
 
     if (needsRecalc)