Enable delta AA by default

The earlier CL doesn't change the flag definition so it's not
turned on yet.

Bug: skia:
Change-Id: Id278ae5fc27d703ab7f6628bed95093d32cd7d0b
TBR: caryclark@google.com, fmalita@chromium.org
Reviewed-on: https://skia-review.googlesource.com/28161
Commit-Queue: Yuqian Li <liyuqian@google.com>
Reviewed-by: Yuqian Li <liyuqian@google.com>
diff --git a/tools/flags/SkCommonFlags.cpp b/tools/flags/SkCommonFlags.cpp
index 19afd10..4ea3a69 100644
--- a/tools/flags/SkCommonFlags.cpp
+++ b/tools/flags/SkCommonFlags.cpp
@@ -72,7 +72,12 @@
                                     "whether it's concave or convex, we consider a path complicated"
                                     "if its number of points is comparable to its resolution.");
 
-DEFINE_bool(deltaAA, false,
+#ifdef SK_SUPPORT_LEGACY_DELTA_AA
+constexpr bool kDefaultDeltaAA = false;
+#else
+constexpr bool kDefaultDeltaAA = true;
+#endif
+DEFINE_bool(deltaAA, kDefaultDeltaAA,
             "If true, use delta anti-aliasing in suitable cases (it overrides forceAnalyticAA.");
 
 DEFINE_bool(forceDeltaAA, false, "Force delta anti-aliasing for all paths.");