Templatize SkToXXX.

include/private/SkTLogic.h

Index: include/private/SkTLogic.h
diff --git a/include/private/SkTLogic.h b/include/private/SkTLogic.h
index b38fd50435cbccfd5de0dbeff15eca9e0d9fdd88..298033ad462e75e29917d960b58b6a1201bd81ae 100644
--- a/include/private/SkTLogic.h
+++ b/include/private/SkTLogic.h
@@ -14,8 +14,6 @@
 #ifndef SkTLogic_DEFINED
 #define SkTLogic_DEFINED
 
-#include "SkTypes.h"
-
 #include <stddef.h>
 #include <stdint.h>
 #include <type_traits>
@@ -42,7 +40,7 @@ template <typename T> using remove_extent_t = typename std::remove_extent<T>::ty
 // On all platforms, variadic functions only exist in the c calling convention.
 // mcvc 2013 introduced __vectorcall, but it wan't until 2015 that it was added to is_function.
 template <typename> struct is_function : std::false_type {};
-#if !defined(SK_BUILD_FOR_WIN)
+#if !defined(WIN32)
 template <typename R, typename... Args> struct is_function<R(Args...)> : std::true_type {};
 #else
 template <typename R, typename... Args> struct is_function<R __cdecl (Args...)> : std::true_type {};
@@ -50,7 +48,7 @@ template <typename R, typename... Args> struct is_function<R __cdecl (Args...)>
 template <typename R, typename... Args> struct is_function<R __stdcall (Args...)> : std::true_type {};
 template <typename R, typename... Args> struct is_function<R __fastcall (Args...)> : std::true_type {};
 #endif
-#if defined(_MSC_VER) && SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
+#if defined(_MSC_VER) && (_M_IX86_FP >= 2 || defined(_M_AMD64) || defined(_M_X64))
 template <typename R, typename... Args> struct is_function<R __vectorcall (Args...)> : std::true_type {};
 #endif
 #endif
@@ -64,6 +62,27 @@ template <typename T> using add_lvalue_reference_t = typename std::add_lvalue_re
 
 template <typename... T> using common_type_t = typename std::common_type<T...>::type;
 
+// Chromium currently requires gcc 4.8.2 or a recent clang compiler, but uses libstdc++4.6.4.
+// Note that Precise actually uses libstdc++4.6.3.
+// Unfortunately, libstdc++ STL before libstdc++4.7 do not define std::underlying_type.
+// Newer gcc and clang compilers have __underlying_type which does not depend on runtime support.
+// See https://gcc.gnu.org/onlinedocs/libstdc++/manual/abi.html for __GLIBCXX__ values.
+// Unfortunately __GLIBCXX__ is a date, but no updates to versions before 4.7 are now anticipated.
+#define SK_GLIBCXX_4_7_0 20120322
+// Updates to versions before 4.7 but released after 4.7 was released.
+#define SK_GLIBCXX_4_5_4 20120702
+#define SK_GLIBCXX_4_6_4 20121127
+#if defined(__GLIBCXX__) && (__GLIBCXX__ <  SK_GLIBCXX_4_7_0 || \
+                             __GLIBCXX__ == SK_GLIBCXX_4_5_4 || \
+                             __GLIBCXX__ == SK_GLIBCXX_4_6_4)
+template <typename T> struct underlying_type {
+    using type = __underlying_type(T);
+};
+#else
+template <typename T> using underlying_type = std::underlying_type<T>;
+#endif
+template <typename T> using underlying_type_t = typename skstd::underlying_type<T>::type;
+
 template <typename S, typename D,
           bool=std::is_void<S>::value || is_function<D>::value || std::is_array<D>::value>
 struct is_convertible_detector {