update SkSmallAllocator to force internal allocations to be 16-byte aligned

include/core/SkTypes.h

Index: include/core/SkTypes.h
diff --git a/include/core/SkTypes.h b/include/core/SkTypes.h
index 5831ba3e80fa1093e681f20341ba3a7ef43e3d82..b9e519195598de44a66a0b407984c2410ed2d30b 100644
--- a/include/core/SkTypes.h
+++ b/include/core/SkTypes.h
@@ -337,6 +337,9 @@ template <typename T, size_t N> char (&SkArrayCountHelper(T (&array)[N]))[N];
 #define SkAlign8(x)     (((x) + 7) >> 3 << 3)
 #define SkIsAlign8(x)   (0 == ((x) & 7))
 
+#define SkAlign16(x)     (((x) + 15) >> 4 << 4)
+#define SkIsAlign16(x)   (0 == ((x) & 15))
+
 #define SkAlignPtr(x)   (sizeof(void*) == 8 ?   SkAlign8(x) :   SkAlign4(x))
 #define SkIsAlignPtr(x) (sizeof(void*) == 8 ? SkIsAlign8(x) : SkIsAlign4(x))