Add flag for SkGpuSurface creation to enable distance fields.

src/gpu/GrDistanceFieldTextContext.cpp

Index: src/gpu/GrDistanceFieldTextContext.cpp
diff --git a/src/gpu/GrDistanceFieldTextContext.cpp b/src/gpu/GrDistanceFieldTextContext.cpp
index 238bcca46b4be737e884672d49edc8724cbce5cf..512420eb672090a205e665a47973fe3dd5892ec6 100755
--- a/src/gpu/GrDistanceFieldTextContext.cpp
+++ b/src/gpu/GrDistanceFieldTextContext.cpp
@@ -33,15 +33,15 @@ static const int kLargeDFFontSize = 128;
 SK_CONF_DECLARE(bool, c_DumpFontCache, "gpu.dumpFontCache", false,
                 "Dump the contents of the font cache before every purge.");
 
+GrDistanceFieldTextContext::GrDistanceFieldTextContext(GrContext* context,
+                                                       const SkDeviceProperties& properties,
+                                                       bool enable)
+                                                    : GrTextContext(context, properties) {
 #if SK_FORCE_DISTANCEFIELD_FONTS
-static const bool kForceDistanceFieldFonts = true;
+    fEnableDFRendering = true;
 #else
-static const bool kForceDistanceFieldFonts = false;
+    fEnableDFRendering = enable;
 #endif
-
-GrDistanceFieldTextContext::GrDistanceFieldTextContext(GrContext* context,
-                                                       const SkDeviceProperties& properties)
-                                                    : GrTextContext(context, properties) {
     fStrike = NULL;
 
     fCurrTexture = NULL;
@@ -56,7 +56,7 @@ GrDistanceFieldTextContext::~GrDistanceFieldTextContext() {
 }
 
 bool GrDistanceFieldTextContext::canDraw(const SkPaint& paint) {
-    if (!kForceDistanceFieldFonts && !paint.isDistanceFieldTextTEMP()) {
+    if (!fEnableDFRendering && !paint.isDistanceFieldTextTEMP()) {
         return false;
     }