Reattach whitespace siblings only when needed

Source/core/dom/Text.cpp

Index: Source/core/dom/Text.cpp
diff --git a/Source/core/dom/Text.cpp b/Source/core/dom/Text.cpp
index ad796131d66ab9fb16c928cb0bfd4b6c74a6595b..c2069449277a875d96e31a372204cb5dd474c207 100644
--- a/Source/core/dom/Text.cpp
+++ b/Source/core/dom/Text.cpp
@@ -276,7 +276,7 @@ bool Text::textRendererIsNeeded(const RenderStyle& style, const RenderObject& pa
         RenderObject* first = parent.slowFirstChild();
         while (first && first->isFloatingOrOutOfFlowPositioned() && maxSiblingsToVisit--)
             first = first->nextSibling();
-        if (!first || NodeRenderingTraversal::nextSiblingRenderer(this) == first)
+        if (!first || first == renderer() || NodeRenderingTraversal::nextSiblingRenderer(this) == first)

[Xianzhu, 2014/11/05 20:15:33]

'!first' is not strictly necessary because first==renderer() can cover it, but
including it seems to improve readability.

             // Whitespace at the start of a block just goes away.  Don't even
             // make a render object for this text.
             return false;
@@ -308,6 +308,26 @@ void Text::attach(const AttachContext& context)
     CharacterData::attach(context);
 }
 
+void Text::reattachIfNeeded(const AttachContext& context)
+{
+    RenderTreeBuilderForText treeBuilder(this);
+    bool hadRenderer = renderer();
+    bool rendererIsNeeded = treeBuilder.rendererIsNeeded();
+    if (rendererIsNeeded == hadRenderer)
+        return;
+
+    // The following is almost the same as Node::attach() except that we create renderer only if needed.
+    // Not calling reattach() to avoid repeated calls to Text::textRendererIsNeeded().
+    AttachContext reattachContext(context);
+    reattachContext.performingReattach = true;
+
+    if (styleChangeType() < NeedsReattachStyleChange)
+        detach(reattachContext);
+    if (rendererIsNeeded)
+        treeBuilder.createRenderer();
+    CharacterData::attach(reattachContext);
+}
+
 void Text::recalcTextStyle(StyleRecalcChange change, Text* nextTextSibling)
 {
     if (RenderText* renderer = this->renderer()) {
@@ -319,7 +339,7 @@ void Text::recalcTextStyle(StyleRecalcChange change, Text* nextTextSibling)
     } else if (needsStyleRecalc() || needsWhitespaceRenderer()) {
         reattach();
         if (this->renderer())
-            reattachWhitespaceSiblings(nextTextSibling);
+            reattachWhitespaceSiblingsIfNeeded(nextTextSibling);
     }
 }