[SkTextBlob] Custom run font record

Instead of using a full-blown SkPaint to store run font info, use a
custom structure.

This saves 96 bytes / run on 64bit platforms.

R=reed@google.com,mtklein@google.com,joshualitt@google.com

Review URL: https://codereview.chromium.org/1070943002
diff --git a/include/core/SkTypes.h b/include/core/SkTypes.h
index 3f4bc2c..9014620 100644
--- a/include/core/SkTypes.h
+++ b/include/core/SkTypes.h
@@ -448,7 +448,7 @@
 
 /** \class SkNoncopyable
 
-SkNoncopyable is the base class for objects that may do not want to
+SkNoncopyable is the base class for objects that do not want to
 be copied. It hides its copy-constructor and its assignment-operator.
 */
 class SK_API SkNoncopyable {