Extend SkFontMgr_Custom to cover ttc, otf, pfb.

src/ports/SkFontMgr_fontconfig.cpp

Index: src/ports/SkFontMgr_fontconfig.cpp
diff --git a/src/ports/SkFontMgr_fontconfig.cpp b/src/ports/SkFontMgr_fontconfig.cpp
index d7570d9354bc9a8ea9284241f1b3e305ae6b6c93..815d9f966a890b95b2a9de6fb7674814944db18b 100644
--- a/src/ports/SkFontMgr_fontconfig.cpp
+++ b/src/ports/SkFontMgr_fontconfig.cpp
@@ -452,6 +452,7 @@ private:
 class SkFontMgr_fontconfig : public SkFontMgr {
     mutable SkAutoFcConfig fFC;
     SkAutoTUnref<SkDataTable> fFamilyNames;
+    SkTypeface_FreeType::Scanner fScanner;
 
     class StyleSet : public SkFontStyleSet {
     public:
@@ -827,7 +828,7 @@ protected:
 
         SkFontStyle style;
         bool isFixedWidth = false;
-        if (!SkTypeface_FreeType::ScanFont(stream, ttcIndex, NULL, &style, &isFixedWidth)) {
+        if (!fScanner.scanFont(stream, ttcIndex, NULL, &style, &isFixedWidth)) {
             return NULL;
         }