Rename flag from "distance field" to "device independent."

Review URL: https://codereview.chromium.org/1322433006
diff --git a/src/gpu/GrAtlasTextContext.cpp b/src/gpu/GrAtlasTextContext.cpp
index 06d6675..3de0ef8 100644
--- a/src/gpu/GrAtlasTextContext.cpp
+++ b/src/gpu/GrAtlasTextContext.cpp
@@ -458,7 +458,7 @@
         return false;
     }
 
-    bool useDFT = fSurfaceProps.isUseDistanceFieldFonts();
+    bool useDFT = fSurfaceProps.isUseDeviceIndependentFonts();
 #if SK_FORCE_DISTANCE_FIELD_TEXT
     useDFT = true;
 #endif