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/GrGpuGL.cpp b/gpu/src/GrGpuGL.cpp
index 721d084..c63c766 100644
--- a/gpu/src/GrGpuGL.cpp
+++ b/gpu/src/GrGpuGL.cpp
@@ -1754,8 +1754,12 @@
                                                 nextTexture->getTexParams();
             GrGLTexture::TexParams newTexParams;
 
-            newTexParams.fFilter = sampler.isFilter() ? GR_GL_LINEAR :
-                                                        GR_GL_NEAREST;
+            if (GrSamplerState::kNearest_Filter == sampler.getFilter()) {
+                newTexParams.fFilter = GR_GL_NEAREST;
+            } else {
+                newTexParams.fFilter = GR_GL_LINEAR;
+            }
+
             newTexParams.fWrapS =
                         GrGLTexture::WrapMode2GLWrap()[sampler.getWrapX()];
             newTexParams.fWrapT =