SimpleFontData::fillGlyphPage should not set zero for missing glyphs

Source/platform/fonts/GlyphPageTreeNode.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 Apple 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 259 matching lines @@
 
                 // Overlay the parent page on the fallback page. Check if the fallback font
                 // has added anything.
                 bool newGlyphs = false;
                 for (unsigned i = 0; i < GlyphPage::size; i++) {
                     if (parentPage->glyphAt(i))
                         m_page->setGlyphDataForIndex(i, parentPage->glyphDataForIndex(i));
                     else  if (fallbackPage->glyphAt(i)) {
                         m_page->setGlyphDataForIndex(i, fallbackPage->glyphDataForIndex(i));
                         newGlyphs = true;
-                    } else
-                        m_page->setGlyphDataForIndex(i, 0, 0);
+                    }
                 }
 
                 if (!newGlyphs)
                     // We didn't override anything, so our override is just the parent page.
                     m_page = parentPage;
             }
         }
     } else {
         // System fallback. Initialized with the parent's page here, as individual
         // entries may use different fonts depending on character. If the Font
@@ skipping 114 matching lines @@
         printf("\nPage %d:\n", it->key);
         showGlyphPageTree(it->key);
     }
 }
 
 void showGlyphPageTree(unsigned pageNumber)
 {
     WebCore::GlyphPageTreeNode::getRoot(pageNumber)->showSubtree();
 }
 #endif