add gamma value to deviceproperties

BUG=skia:

Review URL: https://codereview.chromium.org/652273002
diff --git a/src/gpu/GrDistanceFieldTextContext.cpp b/src/gpu/GrDistanceFieldTextContext.cpp
index 183b83c..04ad59b 100755
--- a/src/gpu/GrDistanceFieldTextContext.cpp
+++ b/src/gpu/GrDistanceFieldTextContext.cpp
@@ -169,8 +169,8 @@
 #else
         SkScalar contrast = 0.5f;
 #endif
-        SkScalar paintGamma = deviceProperties.getGamma();
-        SkScalar deviceGamma = deviceProperties.getGamma();
+        SkScalar paintGamma = deviceProperties.gamma();
+        SkScalar deviceGamma = deviceProperties.gamma();
 
         size = SkScalerContext::GetGammaLUTSize(contrast, paintGamma, deviceGamma,
                                                 &width, &height);
@@ -358,7 +358,7 @@
     flags |= fUseLCDText ? kUseLCD_DistanceFieldEffectFlag : 0;
     flags |= fUseLCDText && ctm.rectStaysRect() ?
     kRectToRect_DistanceFieldEffectFlag : 0;
-    bool useBGR = SkPixelGeometryIsBGR(fDeviceProperties.fPixelGeometry);
+    bool useBGR = SkPixelGeometryIsBGR(fDeviceProperties.pixelGeometry());
     flags |= fUseLCDText && useBGR ? kBGR_DistanceFieldEffectFlag : 0;
     
     // see if we need to create a new effect
@@ -375,7 +375,7 @@
                                                                                    flags));
         } else {
 #ifdef SK_GAMMA_APPLY_TO_A8
-            U8CPU lum = SkColorSpaceLuminance::computeLuminance(fDeviceProperties.getGamma(),
+            U8CPU lum = SkColorSpaceLuminance::computeLuminance(fDeviceProperties.gamma(),
                                                                 filteredColor);
             fCachedGeometryProcessor.reset(GrDistanceFieldTextureEffect::Create(fCurrTexture,
                                                                                 params,