Add AA Analytic Compile Flag (and small fixes)

src/core/SkScan.cpp

Index: src/core/SkScan.cpp
diff --git a/src/core/SkScan.cpp b/src/core/SkScan.cpp
index ceb9ff6e7a418a5e0213b3043d20f1bf9ef23f0a..a7ecf31826aec4d9f61c1fffade68f96366908b8 100644
--- a/src/core/SkScan.cpp
+++ b/src/core/SkScan.cpp
@@ -10,7 +10,11 @@
 #include "SkBlitter.h"
 #include "SkRasterClip.h"
 
-std::atomic<bool> gSkUseAnalyticAA{false};
+#ifdef SK_ANALYTIC_AA
+    std::atomic<bool> gSkUseAnalyticAA{true};
+#else
+    std::atomic<bool> gSkUseAnalyticAA{false};
+#endif
 
 static inline void blitrect(SkBlitter* blitter, const SkIRect& r) {
     blitter->blitRect(r.fLeft, r.fTop, r.width(), r.height());