Special-casing the zero glyph page is unnecessary (Part 2)

https://bugs.webkit.org/show_bug.cgi?id=259257
rdar://112344047

Reviewed by Cameron McCormack.

This is a follow-up to 266052@main. Each glyph page only holds 16 characters, so the
0th glyph page isn't really special. Almost no text will actually use it. So there's
no need to special-case it. (I bet that this special-case wasn't actually created
for performance, but just because of how our HashMaps treat 0 as empty...)

* Source/WebCore/platform/graphics/Font.cpp:
(WebCore::Font::glyphPage const):
* Source/WebCore/platform/graphics/Font.h:

Canonical link: https://commits.webkit.org/266091@main

Source/WebCore/platform/graphics/Font.cpp

@@ -404,11 +404,6 @@ static RefPtr<GlyphPage> createAndFillGlyphPage(unsigned pageNumber, const Font&
 
 const GlyphPage* Font::glyphPage(unsigned pageNumber) const
 {
-    if (!pageNumber) {
-        if (!m_glyphPageZero)
-            m_glyphPageZero = createAndFillGlyphPage(0, *this);
-        return m_glyphPageZero.get();
-    }
     auto addResult = m_glyphPages.add(pageNumber, nullptr);
     if (addResult.isNewEntry)
         addResult.iterator->value = createAndFillGlyphPage(pageNumber, *this);

Source/WebCore/platform/graphics/Font.h

@@ -286,8 +286,7 @@ class Font : public RefCounted<Font> {
 
     const FontPlatformData m_platformData;
 
-    mutable RefPtr<GlyphPage> m_glyphPageZero;
-    mutable HashMap<unsigned, RefPtr<GlyphPage>> m_glyphPages;
+    mutable HashMap<unsigned, RefPtr<GlyphPage>, IntHash<unsigned>, WTF::UnsignedWithZeroKeyHashTraits<unsigned>> m_glyphPages;
     mutable GlyphMetricsMap<float> m_glyphToWidthMap;
     mutable std::unique_ptr<GlyphMetricsMap<FloatRect>> m_glyphToBoundsMap;
     // FIXME: Find a more efficient way to represent std::optional<Path>.