A fix for Issue 5139 "some plane-1 characters are not displayed correctly"....

webkit/port/platform/graphics/GlyphPageTreeNodeWin.cpp

 // Copyright (c) 2008, 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:
 // 
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 186 matching lines @@
     bool have_glyphs = false;
     
     UniscribeHelperTextRun state(buffer, GlyphPage::size * 2, false,
                                  fontData->m_font.hfont(),
                                  fontData->m_font.scriptCache(),
                                  fontData->m_font.scriptFontProperties());
     state.setInhibitLigate(true);
     state.Init();
 
     for (unsigned i = 0; i < GlyphPage::size; i++) {
-        WORD glyph = state.FirstGlyphForCharacter(i);
+        // Each character in this input buffer is a surrogate pair, which
+        // consists of two UChars. So, the offset for its i-th character is
+        // (i * 2).
+        WORD glyph = state.FirstGlyphForCharacter(i * 2);
         if (glyph) {
             have_glyphs = true;
             page->setGlyphDataForIndex(i, glyph, fontData);
         } else {
             // Clear both glyph and fontData fields.
             page->setGlyphDataForIndex(i, 0, 0);
         }
     }
     return have_glyphs;
 }
@@ skipping 13 matching lines @@
         return FillBMPGlyphs(characterBuffer, this, fontData, true);
     } else if (bufferLength == GlyphPage::size * 2) {
         return FillNonBMPGlyphs(characterBuffer, this, fontData);
     } else {
         // TODO: http://b/1007391 make use of offset and length
         return false;
     }
 }
 
 }