Added purge method to SimpleFontData and PlatformFontData.

third_party/WebKit/Source/platform/fonts/SimpleFontData.cpp

Index: third_party/WebKit/Source/platform/fonts/SimpleFontData.cpp
diff --git a/third_party/WebKit/Source/platform/fonts/SimpleFontData.cpp b/third_party/WebKit/Source/platform/fonts/SimpleFontData.cpp
index efed5b9083f72d60fc2b920d60074b69e495437f..ddf9765e553ae6b24eec02d8cc62323adb84659c 100644
--- a/third_party/WebKit/Source/platform/fonts/SimpleFontData.cpp
+++ b/third_party/WebKit/Source/platform/fonts/SimpleFontData.cpp
@@ -447,4 +447,10 @@ bool SimpleFontData::fillGlyphPage(GlyphPage* pageToFill, unsigned offset, unsig
     return haveGlyphs;
 }
 
+void SimpleFontData::purgeMemory()
+{
+    m_glyphToBoundsMap.reset(nullptr);
+    m_platformData.purgeMemory();
+}
+
 } // namespace blink