Implement support for mixed sampled render targets

include/gpu/GrTypes.h

Index: include/gpu/GrTypes.h
diff --git a/include/gpu/GrTypes.h b/include/gpu/GrTypes.h
index 3f02c62bfd07aab21c647c673beef0850a782c32..a3291030773ea3c0424f1bf5df8dd98439dc78d1 100644
--- a/include/gpu/GrTypes.h
+++ b/include/gpu/GrTypes.h
@@ -528,6 +528,21 @@ struct GrBackendTextureDesc {
 ///////////////////////////////////////////////////////////////////////////////
 
 /**
+ * Optional bitfield flags that can be set on GrBackendRenderTargetDesc (below).
+ */
+enum GrBackendRenderTargetFlags {
+    kNone_GrBackendRenderTargetFlags            = 0x0,
+    /**
+     * Which buffers are multisampled (color and stencil, or just stencil?).
+     * The default is both. Note that mixing multisampled and aliased buffers
+     * is only possible if NV_framebuffer_mixed_samples is available.
+     */
+    kStencilMSAAOnly_GrBackendRenderTargetFlags = 0x1,
+};
+
+GR_MAKE_BITFIELD_OPS(GrBackendRenderTargetFlags)
+
+/**
  * Gr can wrap an existing render target created by the client in the 3D API
  * with a GrRenderTarget object. The client is responsible for ensuring that the
  * underlying 3D API object lives at least as long as the GrRenderTarget object
@@ -539,6 +554,7 @@ struct GrBackendTextureDesc {
 
 struct GrBackendRenderTargetDesc {
     GrBackendRenderTargetDesc() { memset(this, 0, sizeof(*this)); }
+    GrBackendRenderTargetFlags      fFlags;
     int                             fWidth;         //<! width in pixels
     int                             fHeight;        //<! height in pixels
     GrPixelConfig                   fConfig;        //<! color format