Change HarfBuzzShaper to use FloatBoxExtent for glyp bounds

Source/platform/fonts/harfbuzz/HarfBuzzShaper.cpp

Index: Source/platform/fonts/harfbuzz/HarfBuzzShaper.cpp
diff --git a/Source/platform/fonts/harfbuzz/HarfBuzzShaper.cpp b/Source/platform/fonts/harfbuzz/HarfBuzzShaper.cpp
index d415fbfc253af942287dcc639f92c2ec348998b7..5d8235721d625e967c708b635e8cc55a68ad6d0f 100644
--- a/Source/platform/fonts/harfbuzz/HarfBuzzShaper.cpp
+++ b/Source/platform/fonts/harfbuzz/HarfBuzzShaper.cpp
@@ -382,10 +382,7 @@ HarfBuzzShaper::HarfBuzzShaper(const Font* font, const TextRun& run, ForTextEmph
     , m_fromIndex(0)
     , m_toIndex(m_run.length())
     , m_forTextEmphasis(forTextEmphasis)
-    , m_minGlyphBoundingBoxX(std::numeric_limits<float>::max())
-    , m_maxGlyphBoundingBoxX(std::numeric_limits<float>::min())
-    , m_minGlyphBoundingBoxY(std::numeric_limits<float>::max())
-    , m_maxGlyphBoundingBoxY(std::numeric_limits<float>::min())
+    , m_glyphBoundingBox(std::numeric_limits<float>::max(), std::numeric_limits<float>::min(), std::numeric_limits<float>::min(), std::numeric_limits<float>::max())
 {
     m_normalizedBuffer = adoptArrayPtr(new UChar[m_run.length() + 1]);
     normalizeCharacters(m_run, m_run.length(), m_normalizedBuffer.get(), &m_normalizedBufferLength);
@@ -906,10 +903,7 @@ void HarfBuzzShaper::setGlyphPositionsForHarfBuzzRun(HarfBuzzRun* currentRun, hb
 
         FloatRect glyphBounds = currentFontData->boundsForGlyph(glyph);
         glyphBounds.move(glyphOrigin.x(), glyphOrigin.y());
-        m_minGlyphBoundingBoxX = std::min(m_minGlyphBoundingBoxX, glyphBounds.x());
-        m_maxGlyphBoundingBoxX = std::max(m_maxGlyphBoundingBoxX, glyphBounds.maxX());
-        m_minGlyphBoundingBoxY = std::min(m_minGlyphBoundingBoxY, glyphBounds.y());
-        m_maxGlyphBoundingBoxY = std::max(m_maxGlyphBoundingBoxY, glyphBounds.maxY());
+        m_glyphBoundingBox.unite(glyphBounds);
         glyphOrigin += FloatSize(advance + offsetX, offsetY);
 
         totalAdvance += advance;