Fixed perf regression by removing tree traversal for text sibling.

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

Index: third_party/WebKit/Source/core/dom/Document.h
diff --git a/third_party/WebKit/Source/core/dom/Document.h b/third_party/WebKit/Source/core/dom/Document.h
index 8e2379b87dbb9f46de569918391676782f842009..99ac211f8e1c1e51c2c72a19d5abb6bb48bfb827 100644
--- a/third_party/WebKit/Source/core/dom/Document.h
+++ b/third_party/WebKit/Source/core/dom/Document.h
@@ -41,6 +41,7 @@
 #include "core/dom/DocumentTiming.h"
 #include "core/dom/ExecutionContext.h"
 #include "core/dom/MutationObserver.h"
+#include "core/dom/Text.h"
 #include "core/dom/TextLinkColors.h"
 #include "core/dom/TreeScope.h"
 #include "core/dom/UserActionElementSet.h"
@@ -51,6 +52,7 @@
 #include "core/frame/HostsUsingFeatures.h"
 #include "core/html/parser/ParserSynchronizationPolicy.h"
 #include "core/page/PageVisibilityState.h"
+#include "core/style/ComputedStyle.h"
 #include "platform/Length.h"
 #include "platform/Timer.h"
 #include "platform/weborigin/KURL.h"
@@ -159,7 +161,6 @@ class StringOrDictionary;
 class StyleEngine;
 class StyleResolver;
 class StyleSheetList;
-class Text;
 class TextAutosizer;
 class Touch;
 class TouchList;
@@ -251,6 +252,17 @@ enum WouldLoadReason {
   WouldLoadReasonEnd
 };
 
+struct StyleRecalcData : public GarbageCollectedFinalized<StyleRecalcData> {

[rune, 2016/11/07 09:43:19]

This is only used for reattachment, right? How about calling it
StyleReattachData or smth. I was worried we store these objects for all elements
being recalc'ed when I first saw it.

Could we perhaps put this class in a separate include file and just forward
declare it in Document.h?

+  StyleRecalcData(RefPtr<ComputedStyle> computedStyle, Text* nextTextSibling)
+      : computedStyle(std::move(computedStyle)),
+        nextTextSibling(nextTextSibling) {}
+
+  RefPtr<ComputedStyle> computedStyle;
+  Member<Text> nextTextSibling;
+
+  DEFINE_INLINE_TRACE() { visitor->trace(nextTextSibling); }
+};
+
 using DocumentClassFlags = unsigned char;
 
 class CORE_EXPORT Document : public ContainerNode,
@@ -345,8 +357,8 @@ class CORE_EXPORT Document : public ContainerNode,
   Range* caretRangeFromPoint(int x, int y);
   Element* scrollingElement();
 
-  void addNonAttachedStyle(Element&, RefPtr<ComputedStyle>);
-  ComputedStyle* getNonAttachedStyle(Element&);
+  void addStyleRecalcData(Element&, StyleRecalcData*);
+  StyleRecalcData* getStyleRecalcData(Element&);
 
   String readyState() const;
 
@@ -1450,7 +1462,7 @@ class CORE_EXPORT Document : public ContainerNode,
   Member<DocumentParser> m_parser;
   Member<ContextFeatures> m_contextFeatures;
 
-  HeapHashMap<Member<Element>, RefPtr<ComputedStyle>> m_nonAttachedStyle;
+  HeapHashMap<Member<Element>, Member<StyleRecalcData>> m_styleRecalcDataMap;

[esprehn, 2016/11/07 22:26:26]

HeapHashMap<Member<Element>, StyleRecalcData>

that way we avoid tons of heap allocations. That produces some waste inside the
map, but it's okay since this is just temporary inside updateStyle.

 
   bool m_wellFormed;