Simplify embeddability test.

src/sfnt/SkOTTable_OS_2.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkOTTable_OS_2_DEFINED
 #define SkOTTable_OS_2_DEFINED
 
 #include "SkOTTable_OS_2_VA.h"
 #include "SkOTTable_OS_2_V0.h"
 #include "SkOTTable_OS_2_V1.h"
 #include "SkOTTable_OS_2_V2.h"
 #include "SkOTTable_OS_2_V3.h"
 #include "SkOTTable_OS_2_V4.h"
 
 #pragma pack(push, 1)
 
 struct SkOTTableOS2 {
-    static const SK_OT_CHAR TAG0 = 'O';
-    static const SK_OT_CHAR TAG1 = 'S';
-    static const SK_OT_CHAR TAG2 = '/';
-    static const SK_OT_CHAR TAG3 = '2';
-    static const SK_OT_ULONG TAG = SkOTTableTAG<SkOTTableOS2>::value;
+    static constexpr SK_OT_CHAR TAG0 = 'O';
+    static constexpr SK_OT_CHAR TAG1 = 'S';
+    static constexpr SK_OT_CHAR TAG2 = '/';
+    static constexpr SK_OT_CHAR TAG3 = '2';
+    static constexpr SK_OT_ULONG TAG = SkOTTableTAG<SkOTTableOS2>::value;
 
     union Version {
         SK_OT_USHORT version;
 
         //original V0 TT
         struct VA : SkOTTableOS2_VA { } vA;
         struct V0 : SkOTTableOS2_V0 { } v0;
         struct V1 : SkOTTableOS2_V1 { } v1;
         struct V2 : SkOTTableOS2_V2 { } v2;
         //makes fsType 0-3 exclusive
         struct V3 : SkOTTableOS2_V3 { } v3;
         //defines fsSelection bits 7-9
         struct V4 : SkOTTableOS2_V4 { } v4;
     } version;
 };
 
 #pragma pack(pop)
 
 
 static_assert(sizeof(SkOTTableOS2::Version::VA) == 68, "sizeof_SkOTTableOS2__VA_not_68");
 static_assert(sizeof(SkOTTableOS2::Version::V0) == 78, "sizeof_SkOTTableOS2__V0_not_78");
 static_assert(sizeof(SkOTTableOS2::Version::V1) == 86, "sizeof_SkOTTableOS2__V1_not_86");
 static_assert(sizeof(SkOTTableOS2::Version::V2) == 96, "sizeof_SkOTTableOS2__V2_not_96");
 static_assert(sizeof(SkOTTableOS2::Version::V3) == 96, "sizeof_SkOTTableOS2__V3_not_96");
 static_assert(sizeof(SkOTTableOS2::Version::V4) == 96, "sizeof_SkOTTableOS2__V4_not_96");
 
 #endif