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/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 9051f04..2a50177 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -423,7 +423,11 @@
         return false;
     }
     grPaint->fSampler.setSampleMode(sampleMode);
-    grPaint->fSampler.setFilter(skPaint.isFilterBitmap());
+    if (skPaint.isFilterBitmap()) {
+        grPaint->fSampler.setFilter(GrSamplerState::kBilinear_Filter);
+    } else {
+        grPaint->fSampler.setFilter(GrSamplerState::kNearest_Filter);
+    }
     grPaint->fSampler.setWrapX(sk_tile_mode_to_grwrap(tileModes[0]));
     grPaint->fSampler.setWrapY(sk_tile_mode_to_grwrap(tileModes[1]));
     if (GrSamplerState::kRadial2_SampleMode == sampleMode) {
@@ -863,7 +867,12 @@
     if (!this->skPaint2GrPaintNoShader(paint, true, &grPaint)) {
         return;
     }
-    grPaint.fSampler.setFilter(paint.isFilterBitmap());
+    if (paint.isFilterBitmap()) {
+        grPaint.fSampler.setFilter(GrSamplerState::kBilinear_Filter);
+    } else {
+        grPaint.fSampler.setFilter(GrSamplerState::kNearest_Filter);
+    }
+    
 
     const int maxTextureDim = fContext->getMaxTextureDimension();
     if (bitmap.getTexture() || (bitmap.width() <= maxTextureDim &&