Simplify GlyphPage initialization for SegmentedFontData

Source/platform/fonts/opentype/OpenTypeVerticalData.cpp

Index: Source/platform/fonts/opentype/OpenTypeVerticalData.cpp
diff --git a/Source/platform/fonts/opentype/OpenTypeVerticalData.cpp b/Source/platform/fonts/opentype/OpenTypeVerticalData.cpp
index 7c8ab6ec5ced4596edcdb9cc800cd19e4e1ee229..c1df3abc0b6a6999fe56b1e7fce197465e9bff54 100644
--- a/Source/platform/fonts/opentype/OpenTypeVerticalData.cpp
+++ b/Source/platform/fonts/opentype/OpenTypeVerticalData.cpp
@@ -560,10 +560,9 @@ void OpenTypeVerticalData::substituteWithVerticalGlyphs(const SimpleFontData* fo
         return;
 
     for (unsigned index = offset, end = offset + length; index < end; ++index) {
-        Glyph glyph = glyphPage->glyphAt(index);
-        if (glyph) {
-            ASSERT(glyphPage->glyphDataForIndex(index).fontData == font);
-            Glyph to = map.get(glyph);
+        GlyphData glyphData = glyphPage->glyphDataForIndex(index);
+        if (glyphData.glyph && glyphData.fontData == font) {
+            Glyph to = map.get(glyphData.glyph);
             if (to)
                 glyphPage->setGlyphDataForIndex(index, to, font);
         }