Add 4x4 downsample filter with 4 bilinear texture reads, use for ssaa.

Review URL: http://codereview.appspot.com/4483042/

git-svn-id: http://skia.googlecode.com/svn/trunk@1250 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gpu/src/GrGpu.cpp b/gpu/src/GrGpu.cpp
index 5fff20f..e18c4a4 100644
--- a/gpu/src/GrGpu.cpp
+++ b/gpu/src/GrGpu.cpp
@@ -755,7 +755,7 @@
     GrSamplerState::kClamp_WrapMode,
     GrSamplerState::kNormal_SampleMode,
     GrMatrix::I(),
-    false);
+    GrSamplerState::kNearest_Filter);