Add onGetFamilyName to SkTypeface.

This speeds up and documents this particular feature of SkTypeface
and also frees up SkFontDescriptor to be used only in serialization.

R=reed@google.com

Author: bungeman@google.com

Review URL: https://codereview.chromium.org/574873002
diff --git a/src/ports/SkFontHost_mac.cpp b/src/ports/SkFontHost_mac.cpp
index 3c73493..5386ac3 100755
--- a/src/ports/SkFontHost_mac.cpp
+++ b/src/ports/SkFontHost_mac.cpp
@@ -452,6 +452,7 @@
 
     virtual int onGetUPEM() const SK_OVERRIDE;
     virtual SkStream* onOpenStream(int* ttcIndex) const SK_OVERRIDE;
+    virtual void onGetFamilyName(SkString* familyName) const SK_OVERRIDE;
     virtual SkTypeface::LocalizedStrings* onCreateFamilyNameIterator() const SK_OVERRIDE;
     virtual int onGetTableTags(SkFontTableTag tags[]) const SK_OVERRIDE;
     virtual size_t onGetTableData(SkFontTableTag, size_t offset,
@@ -1900,6 +1901,10 @@
     return str->c_str();
 }
 
+void SkTypeface_Mac::onGetFamilyName(SkString* familyName) const {
+    get_str(CTFontCopyFamilyName(fFontRef), familyName);
+}
+
 void SkTypeface_Mac::onGetFontDescriptor(SkFontDescriptor* desc,
                                          bool* isLocalStream) const {
     SkString tmpStr;