A few more small changes to make GrAtlasTextBlob nearly self contained

src/gpu/text/GrTextUtils.cpp

Index: src/gpu/text/GrTextUtils.cpp
diff --git a/src/gpu/text/GrTextUtils.cpp b/src/gpu/text/GrTextUtils.cpp
index 364ab46ccb39cfed528cadd7eeca18958ad3e6e6..66a0005f949fbd1f87a0a54842bf9fa4c469a675 100644
--- a/src/gpu/text/GrTextUtils.cpp
+++ b/src/gpu/text/GrTextUtils.cpp
@@ -236,8 +236,7 @@ void GrTextUtils::InitDistanceFieldPaint(GrAtlasTextBlob* blob,
     // against these values to decide if we can reuse or not(ie, will a given scale change our mip
     // level)
     SkASSERT(dfMaskScaleFloor <= scaledTextSize && scaledTextSize <= dfMaskScaleCeil);
-    blob->fMaxMinScale = SkMaxScalar(dfMaskScaleFloor / scaledTextSize, blob->fMaxMinScale);
-    blob->fMinMaxScale = SkMinScalar(dfMaskScaleCeil / scaledTextSize, blob->fMinMaxScale);
+    blob->setMinAndMaxScale(dfMaskScaleFloor / scaledTextSize, dfMaskScaleCeil / scaledTextSize);
 
     skPaint->setLCDRenderText(false);
     skPaint->setAutohinted(false);