Set analytic AA as default.

src/core/SkSRGB.h

Index: src/core/SkSRGB.h
diff --git a/src/core/SkSRGB.h b/src/core/SkSRGB.h
index a12ce9615db8da5631e723b503e3968a8e614c4c..b2ed03f0f1a0fc49066eaccead612ace282b253f 100644
--- a/src/core/SkSRGB.h
+++ b/src/core/SkSRGB.h
@@ -61,7 +61,8 @@ template <int N>
 static inline SkNx<N,int> sk_linear_to_srgb_noclamp(const SkNx<N,float>& x) {
     auto f = sk_linear_to_srgb_needs_trunc(x);
     for (int i = 0; i < 4; i++) {
-        SkASSERTF(0.0f <= f[i] && f[i] < 256.0f, "f[%d] was %g, outside [0,256)\n", i, f[i]);
+        // Turn this assert off for now because srgb conversions may end up in rgb > a
+        // SkASSERTF(0.0f <= f[i] && f[i] < 256.0f, "f[%d] was %g, outside [0,256)\n", i, f[i]);

[mtklein_C, 2016/11/02 18:48:19]

There's a slightly better solution, which is to delete this function completely,
and edit SkRasterPipeline_opts.h to call sk_linear_to_srgb() instead of
sk_linear_to_srgb_noclamp().

If you don't want to complicate this CL with that, that's fine.  I can land that
change first or as a follow up.

[liyuqian, 2016/11/02 19:33:11]

Thank you! I saw your follow up CL. Feel free to land it first as I'm still
debugging the serialize tests issue.

     }
     return SkNx_cast<int>(f);
 }