Make GPU linear gradients do bilinear filtering.

This will require GM (and webkit) rebaselines.
Review URL: https://codereview.appspot.com/6431048

git-svn-id: http://skia.googlecode.com/svn/trunk@4680 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 4e3baa3..c8e3440 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -610,11 +610,7 @@
             break;
         case SkShader::kLinear_BitmapType:
             sampler->setCustomStage(SkNEW_ARGS(GrLinearGradient, (texture)))->unref();
-            if (skPaint.isFilterBitmap()) {
-                sampler->setFilter(GrSamplerState::kBilinear_Filter);
-            } else {
-                sampler->setFilter(GrSamplerState::kNearest_Filter);
-            }
+            sampler->setFilter(GrSamplerState::kBilinear_Filter);
             break;
         default:
             if (skPaint.isFilterBitmap()) {