Create MSAA render target for blur mask texture

src/gpu/SkGpuDevice.cpp

Index: src/gpu/SkGpuDevice.cpp
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 7ce3446b72e59289f8741fd20bf8355ae3bfd4a3..5be3c80f2e660970b913fe09f5cb5bb9880896f2 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -21,6 +21,7 @@
 #include "GrRecordReplaceDraw.h"
 #include "GrStrokeInfo.h"
 #include "GrTracing.h"
+#include "GrGpu.h"
 
 #include "SkGrTexturePixelRef.h"
 
@@ -647,10 +648,15 @@ bool create_mask_GPU(GrContext* context,
     desc.fFlags = kRenderTarget_GrTextureFlagBit;
     desc.fWidth = SkScalarCeilToInt(maskRect.width());
     desc.fHeight = SkScalarCeilToInt(maskRect.height());
+    // try multisampled target if possible

[bsalomon, 2014/10/02 16:59:16]

Why don't we just pass the sample count of the SkGpuDevice's GrRenderTarget here
and use it?

That's what we do for saveLayer (the GrRT created for the layer copies the
sample count of the base SkGpuDevice's GrRT).

+    int maxSampleCnt = context->getGpu()->caps()->maxSampleCount();
+    desc.fSampleCnt = maxSampleCnt >= 4 ? 4 : maxSampleCnt;
     // We actually only need A8, but it often isn't supported as a
     // render target so default to RGBA_8888
     desc.fConfig = kRGBA_8888_GrPixelConfig;
-    if (context->isConfigRenderable(kAlpha_8_GrPixelConfig, false)) {
+
+    bool msaa = desc.fSampleCnt > 0;
+    if (context->isConfigRenderable(kAlpha_8_GrPixelConfig, msaa)) {
         desc.fConfig = kAlpha_8_GrPixelConfig;
     }