Add flag for SkGpuSurface creation to enable distance fields.

BUG=skia:2173
R=bsalomon@google.com, reed@google.com, bungeman@google.com

Author: jvanverth@google.com

Review URL: https://codereview.chromium.org/261783004

git-svn-id: http://skia.googlecode.com/svn/trunk@14525 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 60b4e7c..714a6da 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -190,7 +190,9 @@
     fContext = context;
     fContext->ref();
 
-    fMainTextContext = SkNEW_ARGS(GrDistanceFieldTextContext, (fContext, fLeakyProperties));
+    bool useDFFonts = !!(flags & kDFFonts_Flag);
+    fMainTextContext = SkNEW_ARGS(GrDistanceFieldTextContext, (fContext, fLeakyProperties,
+                                                               useDFFonts));
     fFallbackTextContext = SkNEW_ARGS(GrBitmapTextContext, (fContext, fLeakyProperties));
 
     fRenderTarget = NULL;