Use removeFontFace to avoid resetting fontSelector.

Source/core/css/FontFaceCache.cpp

 /*
  * Copyright (C) 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 89 matching lines @@
         if (familyFontFaces->isEmpty())
             m_fontFaces.remove(fontFacesIter);
     }
     m_fonts.clear();
     if (cssConnected)
         m_cssConnectedFontFaces.remove(fontFace);
 
     ++m_version;
 }
 
+void FontFaceCache::clear()
+{
+    for (StyleRuleToFontFace::iterator it = m_styleRuleToFontFace.begin(); it != m_styleRuleToFontFace.end(); ++it)
+        removeFontFace(it->value.get(), true);
+    m_styleRuleToFontFace.clear();
+}
+
 static inline bool compareFontFaces(CSSSegmentedFontFace* first, CSSSegmentedFontFace* second, FontTraitsMask desiredTraitsMask)
 {
     FontTraitsMask firstTraitsMask = first->traitsMask();
     FontTraitsMask secondTraitsMask = second->traitsMask();
 
     bool firstHasDesiredVariant = firstTraitsMask & desiredTraitsMask & FontVariantMask;
     bool secondHasDesiredVariant = secondTraitsMask & desiredTraitsMask & FontVariantMask;
 
     if (firstHasDesiredVariant != secondHasDesiredVariant)
         return firstHasDesiredVariant;
@@ skipping 89 matching lines @@
             if ((traitsMask & FontVariantNormalMask) && !(candidateTraitsMask & FontVariantNormalMask))
                 continue;
             if (!face || compareFontFaces(candidate, face.get(), traitsMask))
                 face = candidate;
         }
     }
     return face.get();
 }
 
 }