Make GrRenderTarget[(Proxy)|(Context)]? advertise a "full scene aa type".

Bug: skia:
Change-Id: I24549604e8305028e34e0022bfef992a8e8c33f7
Reviewed-on: https://skia-review.googlesource.com/16230
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
diff --git a/gm/windowrectangles.cpp b/gm/windowrectangles.cpp
index 7083487..5f569dd 100644
--- a/gm/windowrectangles.cpp
+++ b/gm/windowrectangles.cpp
@@ -188,7 +188,7 @@
     const GrReducedClip reducedClip(stack, SkRect::Make(kCoverRect), kNumWindows);
 
     GrPaint paint;
-    if (!rtc->isStencilBufferMultisampled()) {
+    if (GrFSAAType::kNone == rtc->fsaaType()) {
         paint.setColor4f(GrColor4f(0, 0.25f, 1, 1));
         this->visualizeAlphaMask(ctx, rtc, reducedClip, std::move(paint));
     } else {