Implement style invalidation tree walk for targeted style recalc upon class change.

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index e3199112cca649bf8ae7e40a0ba871602fad2a2f..b2b18b0b9ed28ac3357e8d7e5695962ecffdeb70 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -1528,7 +1528,7 @@ PassRefPtr<TreeWalker> Document::createTreeWalker(Node* root, unsigned whatToSho
 
 bool Document::shouldCallRecalcStyleForDocument()
 {
-    return needsStyleRecalc() || childNeedsStyleRecalc() || childNeedsDistributionRecalc() || !m_useElementsNeedingUpdate.isEmpty();
+    return needsStyleRecalc() || childNeedsStyleRecalc() || childNeedsDistributionRecalc() || !m_useElementsNeedingUpdate.isEmpty() || childNeedsStyleInvalidation();
 }
 
 void Document::scheduleStyleRecalc()
@@ -1570,6 +1570,19 @@ void Document::updateDistributionIfNeeded()
     recalcDistribution();
 }
 
+void Document::updateNeedsStyleRecalcStateIfNeeded()
+{
+    if (!childNeedsStyleInvalidation())
+        return;
+    TRACE_EVENT0("webkit", "Document::computeNeedsStyleRecalcState");
+    if (!styleResolver()) {

[esprehn, 2014/01/28 00:11:34]

This isn't right, the resolver can get thrown away you'll miss doing
invalidations.

[chrishtr, 2014/01/28 01:11:55]

Added FIXME.

+        clearChildNeedsStyleInvalidation();
+        return;
+    }
+
+    styleResolver()->ensureRuleFeatureSet().computeStyleInvalidation(this);

[esprehn, 2014/01/28 00:11:34]

This can't work, the resolver can get thrown away. You either need to move the
logic to the StyleEngine or get rid of the throw away timer.

[chrishtr, 2014/01/28 01:11:55]

Added FIXME.

+}
+
 void Document::updateDistributionForNodeIfNeeded(Node* node)
 {
     if (node->inDocument()) {
@@ -1658,6 +1671,7 @@ void Document::inheritHtmlAndBodyElementStyles(StyleRecalcChange change)
     }
 }
 
+// FIXME: need a better name than recalcStyle. It's performing style invalidation, style recalc, and distribution.
 void Document::recalcStyle(StyleRecalcChange change)
 {
     // we should not enter style recalc while painting
@@ -1675,6 +1689,7 @@ void Document::recalcStyle(StyleRecalcChange change)
 
     InspectorInstrumentationCookie cookie = InspectorInstrumentation::willRecalculateStyle(this);
 
+    updateNeedsStyleRecalcStateIfNeeded();

[esprehn, 2014/01/28 00:11:34]

This should be the last of these three steps, the updateUseShadowTrees() step
can mutate the DOM.

[chrishtr, 2014/01/28 01:11:55]

Done.

     updateDistributionIfNeeded();
     updateUseShadowTrees();
 
@@ -1779,7 +1794,7 @@ void Document::updateStyleForNodeIfNeeded(Node* node)
     // the path from 'node' to the root needs style recalc.
 
     // Global needed.
-    bool needsRecalc = needsStyleRecalc() || childNeedsDistributionRecalc() || !m_useElementsNeedingUpdate.isEmpty();
+    bool needsRecalc = needsStyleRecalc() || childNeedsDistributionRecalc() || !m_useElementsNeedingUpdate.isEmpty() || childNeedsStyleInvalidation();
 
     // On the path.
     for (Node* ancestor = node; ancestor && !needsRecalc; ancestor = ancestor->parentOrShadowHostNode())