Refactor SkGrFontScaler and SkGrFontKey into non-virtual versions.

This is a pre-cleanup for another change, but has the side benefit of making
the code simpler in general.

No perf increase, despite removing virtual functions.

R=bsalomon@google.com, egdaniel@google.com

Author: jvanverth@google.com

Review URL: https://codereview.chromium.org/385263002
diff --git a/src/gpu/GrTextStrike_impl.h b/src/gpu/GrTextStrike_impl.h
index dcfc04a..1dd623d 100644
--- a/src/gpu/GrTextStrike_impl.h
+++ b/src/gpu/GrTextStrike_impl.h
@@ -13,7 +13,7 @@
 
 class GrFontCache::Key {
 public:
-    explicit Key(const GrKey* fontScalarKey) {
+    explicit Key(const GrFontDescKey* fontScalarKey) {
         fFontScalerKey = fontScalarKey;
     }
 
@@ -27,7 +27,7 @@
     }
 
 private:
-    const GrKey* fFontScalerKey;
+    const GrFontDescKey* fFontScalerKey;
 };
 
 void GrFontCache::detachStrikeFromList(GrTextStrike* strike) {