Revert of Remove unused FontPlatformDataHarfBuzz::emSizeInFontUnits

Source/platform/fonts/harfbuzz/FontPlatformDataHarfBuzz.cpp

Index: Source/platform/fonts/harfbuzz/FontPlatformDataHarfBuzz.cpp
diff --git a/Source/platform/fonts/harfbuzz/FontPlatformDataHarfBuzz.cpp b/Source/platform/fonts/harfbuzz/FontPlatformDataHarfBuzz.cpp
index fee331d456f43fefde5578e10c87b20d2ecb4ea8..5044875f6c66488a8c788ff1c5ef38ba0def9cea 100644
--- a/Source/platform/fonts/harfbuzz/FontPlatformDataHarfBuzz.cpp
+++ b/Source/platform/fonts/harfbuzz/FontPlatformDataHarfBuzz.cpp
@@ -79,6 +79,7 @@
 
 FontPlatformData::FontPlatformData(WTF::HashTableDeletedValueType)
     : m_textSize(0)
+    , m_emSizeInFontUnits(0)
     , m_syntheticBold(false)
     , m_syntheticItalic(false)
     , m_orientation(Horizontal)
@@ -88,6 +89,7 @@
 
 FontPlatformData::FontPlatformData()
     : m_textSize(0)
+    , m_emSizeInFontUnits(0)
     , m_syntheticBold(false)
     , m_syntheticItalic(false)
     , m_orientation(Horizontal)
@@ -97,6 +99,7 @@
 
 FontPlatformData::FontPlatformData(float textSize, bool syntheticBold, bool syntheticItalic)
     : m_textSize(textSize)
+    , m_emSizeInFontUnits(0)
     , m_syntheticBold(syntheticBold)
     , m_syntheticItalic(syntheticItalic)
     , m_orientation(Horizontal)
@@ -108,6 +111,7 @@
     : m_typeface(src.m_typeface)
     , m_family(src.m_family)
     , m_textSize(src.m_textSize)
+    , m_emSizeInFontUnits(src.m_emSizeInFontUnits)
     , m_syntheticBold(src.m_syntheticBold)
     , m_syntheticItalic(src.m_syntheticItalic)
     , m_orientation(src.m_orientation)
@@ -121,6 +125,7 @@
     : m_typeface(tf)
     , m_family(family)
     , m_textSize(textSize)
+    , m_emSizeInFontUnits(0)
     , m_syntheticBold(syntheticBold)
     , m_syntheticItalic(syntheticItalic)
     , m_orientation(orientation)
@@ -133,6 +138,7 @@
     : m_typeface(src.m_typeface)
     , m_family(src.m_family)
     , m_textSize(textSize)
+    , m_emSizeInFontUnits(src.m_emSizeInFontUnits)
     , m_syntheticBold(src.m_syntheticBold)
     , m_syntheticItalic(src.m_syntheticItalic)
     , m_orientation(src.m_orientation)
@@ -144,6 +150,15 @@
 
 FontPlatformData::~FontPlatformData()
 {
+}
+
+int FontPlatformData::emSizeInFontUnits() const
+{
+    if (m_emSizeInFontUnits)
+        return m_emSizeInFontUnits;
+
+    m_emSizeInFontUnits = m_typeface->getUnitsPerEm();
+    return m_emSizeInFontUnits;
 }
 
 FontPlatformData& FontPlatformData::operator=(const FontPlatformData& src)
@@ -156,6 +171,7 @@
     m_harfBuzzFace = nullptr;
     m_orientation = src.m_orientation;
     m_style = src.m_style;
+    m_emSizeInFontUnits = src.m_emSizeInFontUnits;
 
     return *this;
 }