detach blur result texture when it is the same texture used to render path mask

src/gpu/SkGpuDevice.cpp

Index: src/gpu/SkGpuDevice.cpp
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 3fa13a7df9abd6b7b5b5ee220d3f4210ef362b39..7bba41f60aa42f7dc21e2e5ff71500a09076d2ef 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -951,8 +951,17 @@ void SkGpuDevice::drawPath(const SkDraw& draw, const SkPath& origSrcPath,
                 GrTexture* filtered;
 
                 if (paint.getMaskFilter()->filterMaskGPU(mask.texture(), maskRect, &filtered, true)) {
+                    // filterMaskGPU gives us ownership of a ref to the result
                     SkAutoTUnref<GrTexture> atu(filtered);
 
+                    // If the scratch texture that we used as the filter src also holds the filter
+                    // result then we must detach so that this texture isn't recycled for a later
+                    // draw.
+                    if (filtered == mask.texture()) {
+                        mask.detach();
+                        filtered->unref(); // detach transfers GrAutoScratchTexture's ref to us.
+                    }
+
                     if (draw_mask(fContext, maskRect, &grPaint, filtered)) {
                         // This path is completely drawn
                         return;