Fix   fallback glyph lookup

Source/platform/fonts/Font.cpp

Index: Source/platform/fonts/Font.cpp
diff --git a/Source/platform/fonts/Font.cpp b/Source/platform/fonts/Font.cpp
index a45007103723194869d91cbda93eb767f5ed9d96..aa087069dcd1202865b9e157dacb175a2be0e576 100644
--- a/Source/platform/fonts/Font.cpp
+++ b/Source/platform/fonts/Font.cpp
@@ -524,14 +524,15 @@ GlyphData Font::glyphDataForCharacter(UChar32& c, bool mirror, bool normalizeSpa
         }
         if (characterFontData) {
             // Got the fallback glyph and font.
-            GlyphPage* fallbackPage = GlyphPageTreeNode::getRootChild(characterFontData.get(), pageNumber)->page();
-            GlyphData data = fallbackPage && fallbackPage->glyphForCharacter(c) ? fallbackPage->glyphDataForCharacter(c) : characterFontData->missingGlyphData();
+            unsigned pageNumberForRendering = characterToRender / GlyphPage::size;
+            GlyphPage* fallbackPage = GlyphPageTreeNode::getRootChild(characterFontData.get(), pageNumberForRendering)->page();
+            GlyphData data = fallbackPage && fallbackPage->glyphForCharacter(characterToRender) ? fallbackPage->glyphDataForCharacter(characterToRender) : characterFontData->missingGlyphData();
             // Cache it so we don't have to do system fallback again next time.
             if (variant == NormalVariant) {
                 page->setGlyphDataForCharacter(c, data.glyph, data.fontData);
                 data.fontData->setMaxGlyphPageTreeLevel(std::max(data.fontData->maxGlyphPageTreeLevel(), node->level()));
-                if (data.fontData->platformData().isVerticalAnyUpright() && !data.fontData->isTextOrientationFallback() && !Character::isCJKIdeographOrSymbol(c))
-                    return glyphDataForNonCJKCharacterWithGlyphOrientation(c, m_fontDescription.isVerticalUpright(c), data, pageNumber);
+                if (data.fontData->platformData().isVerticalAnyUpright() && !data.fontData->isTextOrientationFallback() && !Character::isCJKIdeographOrSymbol(characterToRender))
+                    return glyphDataForNonCJKCharacterWithGlyphOrientation(characterToRender, m_fontDescription.isVerticalUpright(characterToRender), data, pageNumberForRendering);
             }
             return data;
         }