Partially restore small-T optimization for very small (empty) T.

src/utils/SkTLogic.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
  *
  * This header provides some of the helpers (std::integral_constant) and
  * type transformations (std::conditional) which will become available with
  * C++11 in the type_traits header.
@@ skipping 12 matching lines @@
  */
 template <typename T, T v> struct SkTIntegralConstant {
     static const T value = v;
     typedef T value_type;
     typedef SkTIntegralConstant<T, v> type;
 };
 
 /** Convenience specialization of SkTIntegralConstant. */
 template <bool b> struct SkTBool : SkTIntegralConstant<bool, b> { };
 
+/** Pre-C++11 version of std::is_empty<T>. */
+template <typename T>
+class SkTIsEmpty {
+    struct Derived : public T { char unused; };
+public:
+    static const bool value = sizeof(Derived) == sizeof(char);
+};
+
 /** Pre-C++11 version of std::true_type. */
 typedef SkTBool<true> SkTrue;
 
 /** Pre-C++11 version of std::false_type. */
 typedef SkTBool<false> SkFalse;
 
 /** SkTIf_c::type = (condition) ? T : F;
  *  Pre-C++11 version of std::conditional.
  */
 template <bool condition, typename T, typename F> struct SkTIf_c {
@@ skipping 50 matching lines @@
 #define SK_CREATE_TYPE_DETECTOR(type)                                   \
 template <typename T>                                                   \
 class HasType_##type {                                                  \
     template <typename U> static uint8_t func(typename U::type*);       \
     template <typename U> static uint16_t func(...);                    \
 public:                                                                 \
     static const bool value = sizeof(func<T>(NULL)) == sizeof(uint8_t); \
 }
 
 #endif