Enable blend optimizations with instanced draws

include/private/GrInstancedPipelineInfo.h

Index: include/private/GrInstancedPipelineInfo.h
diff --git a/include/private/GrInstancedPipelineInfo.h b/include/private/GrInstancedPipelineInfo.h
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index 0000000000000000000000000000000000000000..f12b89fc6b80665b2a8552bbf3e19cb4834eae19
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+++ b/include/private/GrInstancedPipelineInfo.h
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+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrGrInstancedPipelineInfo_DEFINED
+#define GrGrInstancedPipelineInfo_DEFINED
+
+#include "GrRenderTarget.h"
+
+/**
+ * Provides info about the pipeline that GrInstancedRendering needs in order to select appropriate
+ * drawing algorithms.
+ */
+struct GrInstancedPipelineInfo {
+    GrInstancedPipelineInfo(const GrRenderTarget* rt)
+        : fIsMultisampled(rt->isStencilBufferMultisampled()),
+          fIsMixedSampled(rt->hasMixedSamples()),
+          fIsRenderingToFloat(GrPixelConfigIsFloatingPoint(rt->desc().fConfig)),
+          fColorDisabled(false),
+          fDrawingShapeToStencil(false),
+          fCanDiscard(false) {
+    }
+
+    bool canUseCoverageAA() const {
+        return !fIsMultisampled || (fIsMixedSampled && !fDrawingShapeToStencil);
+    }
+
+    bool fIsMultisampled         : 1;
+    bool fIsMixedSampled         : 1;
+    bool fIsRenderingToFloat     : 1;
+    bool fColorDisabled          : 1;
+    /**
+     * Indicates that the instanced renderer should take extra precautions to ensure the shape gets
+     * drawn correctly to the stencil buffer (e.g. no coverage AA). NOTE: this does not mean a
+     * stencil test is or is not active.
+     */
+    bool fDrawingShapeToStencil  : 1;
+    /**
+     * Indicates that the instanced renderer can use processors with discard instructions. This
+     * should not be set if the shader will use derivatives, automatic mipmap LOD, or other features
+     * that depend on neighboring pixels. Some draws will fail to create if this is not set.
+     */
+    bool fCanDiscard             : 1;
+};
+
+#endif