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

Source/core/html/parser/HTMLTreeBuilder.cpp

Index: Source/core/html/parser/HTMLTreeBuilder.cpp
diff --git a/Source/core/html/parser/HTMLTreeBuilder.cpp b/Source/core/html/parser/HTMLTreeBuilder.cpp
index 2c2bf920db72442114442757b0bc0a83ed71a16c..41f8e1938079983b9ca999830e6c11a54e25afa2 100644
--- a/Source/core/html/parser/HTMLTreeBuilder.cpp
+++ b/Source/core/html/parser/HTMLTreeBuilder.cpp
@@ -402,7 +402,7 @@
 
     // Any non-character token needs to cause us to flush any pending text immediately.
     // NOTE: flush() can cause any queued tasks to execute, possibly re-entering the parser.
-    m_tree.flush();
+    m_tree.flush(FlushAlways);
     m_shouldSkipLeadingNewline = false;
 
     switch (token->type()) {
@@ -2689,7 +2689,7 @@
         return;
     }
 
-    m_tree.flush();
+    m_tree.flush(FlushAlways);
     HTMLStackItem* adjustedCurrentNode = adjustedCurrentStackItem();
 
     switch (token->type()) {