Revert of Revert of HTMLConstructionSite: avoid n^2 running time for large scripts.

Source/core/html/parser/HTMLDocumentParser.cpp

Index: Source/core/html/parser/HTMLDocumentParser.cpp
diff --git a/Source/core/html/parser/HTMLDocumentParser.cpp b/Source/core/html/parser/HTMLDocumentParser.cpp
index 711715617e9eb85849c9b775a231362b6a6b99c8..3d7d7a47589d0683200fadf6df8065cd30e5d01b 100644
--- a/Source/core/html/parser/HTMLDocumentParser.cpp
+++ b/Source/core/html/parser/HTMLDocumentParser.cpp
@@ -498,9 +498,10 @@
         ASSERT(!m_token);
     }
 
-    // Make sure any pending text nodes are emitted before returning.
+    // Make sure all required pending text nodes are emitted before returning.
+    // This leaves "script", "style" and "svg" nodes text nodes intact.
     if (!isStopped())
-        m_treeBuilder->flush();
+        m_treeBuilder->flush(FlushIfAtTextLimit);
 }
 
 void HTMLDocumentParser::pumpPendingSpeculations()
@@ -635,7 +636,7 @@
     // There should only be PendingText left since the tree-builder always flushes
     // the task queue before returning. In case that ever changes, crash.
     if (mode == ForceSynchronous)
-        m_treeBuilder->flush();
+        m_treeBuilder->flush(FlushAlways);
     RELEASE_ASSERT(!isStopped());
 
     if (session.needsYield)