Revert of Move vertex buffer setup out of drawPackedGlyph(). (https://codereview.chromium.org/414573002/)

Reason for revert:
Breaking Ubuntu and Windows bots.

Original issue's description:
> Move vertex buffer setup out of drawPackedGlyph().
>
> This gets a very welcome ~10% speedup on my Mac.
>
> Committed: https://skia.googlesource.com/skia/+/1d38619389cc1100bd516b9acbf17b7bd42d33ce

R=bsalomon@google.com
TBR=bsalomon@google.com
NOTREECHECKS=true
NOTRY=true

Author: jvanverth@google.com

Review URL: https://codereview.chromium.org/419943002
diff --git a/src/gpu/GrDistanceFieldTextContext.h b/src/gpu/GrDistanceFieldTextContext.h
index 77e56c6..3a602f0 100644
--- a/src/gpu/GrDistanceFieldTextContext.h
+++ b/src/gpu/GrDistanceFieldTextContext.h
@@ -48,7 +48,8 @@
         kDefaultRequestedVerts   = kDefaultRequestedGlyphs * 4,
     };
 
-    void*                   fVertices;
+    SkPoint*                fVertices;
+    int32_t                 fMaxVertices;
     GrTexture*              fCurrTexture;
     int                     fCurrVertex;
 };