Revert of Add a FOUC painting test.

Source/core/dom/Document.h

Index: Source/core/dom/Document.h
diff --git a/Source/core/dom/Document.h b/Source/core/dom/Document.h
index a9a590982f3fdeabefe7e00fd4187138257828cb..bbe68f965dac9555a952bade4edbecde41b85551 100644
--- a/Source/core/dom/Document.h
+++ b/Source/core/dom/Document.h
@@ -1035,8 +1035,8 @@
 
     // Used by unit tests so that all parsing will be main thread for
     // controlling parsing and chunking precisely.
-    static void setThreadedParsingEnabledForTesting(bool);
-    static bool threadedParsingEnabledForTesting();
+    static void setThreadedParsingEnabledForUnitTestsOnly(bool enabled);
+    static bool threadedParsingEnabledForUnitTestsOnly();
 
     void incrementNodeCount() { m_nodeCount++; }
     void decrementNodeCount()