Avoid N^2 walk placing renderers when building the render tree

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 f0c0158df1b2d5b0b3c013523a22aa2b242301ce..3347c73af6c260ee732026bb83958b6451b724a4 100644
--- a/Source/core/dom/Text.cpp
+++ b/Source/core/dom/Text.cpp
@@ -216,7 +216,9 @@ bool Text::textRendererIsNeeded(const NodeRenderingContext& context)
     
     if (context.style()->preserveNewline()) // pre/pre-wrap/pre-line always make renderers.
         return true;
-    
+
+    // FIXME: We should resolve this function's dependencies on next and previous renderers
+    // lazily to avoid potentially N^2 walks through the DOM.
     RenderObject* prev = context.previousRenderer();
     if (prev && prev->isBR()) // <span><br/> <br/></span>
         return false;