Remove base::is_*assignable as these are now in the linux sysroot.

base/template_util.h

Index: base/template_util.h
diff --git a/base/template_util.h b/base/template_util.h
index 42552107cfbc148758c4d2e5ed5caa0078f25507..10154dbbeb9ce6e6cc5cc0d07634e217760e7237 100644
--- a/base/template_util.h
+++ b/base/template_util.h
@@ -51,46 +51,8 @@ template <class T> struct is_non_const_reference : std::false_type {};
 template <class T> struct is_non_const_reference<T&> : std::true_type {};
 template <class T> struct is_non_const_reference<const T&> : std::false_type {};
 
-// is_assignable
-
 namespace internal {
 
-template <typename First, typename Second>
-struct SelectSecond {
-  using type = Second;
-};
-
-struct Any {
-  Any(...);
-};
-
-// True case: If |Lvalue| can be assigned to from |Rvalue|, then the return
-// value is a true_type.
-template <class Lvalue, class Rvalue>
-typename internal::SelectSecond<
-    decltype((std::declval<Lvalue>() = std::declval<Rvalue>())),
-    std::true_type>::type
-IsAssignableTest(Lvalue&&, Rvalue&&);
-
-// False case: Otherwise the return value is a false_type.
-template <class Rvalue>
-std::false_type IsAssignableTest(internal::Any, Rvalue&&);
-
-// Default case: Neither Lvalue nor Rvalue is void. Uses IsAssignableTest to
-// determine the type of IsAssignableImpl.
-template <class Lvalue,
-          class Rvalue,
-          bool = std::is_void<Lvalue>::value || std::is_void<Rvalue>::value>
-struct IsAssignableImpl
-    : public std::common_type<decltype(
-          internal::IsAssignableTest(std::declval<Lvalue>(),
-                                     std::declval<Rvalue>()))>::type {};
-
-// Void case: Either Lvalue or Rvalue is void. Then the type of IsAssignableTest
-// is false_type.
-template <class Lvalue, class Rvalue>
-struct IsAssignableImpl<Lvalue, Rvalue, true> : public std::false_type {};
-
 // Uses expression SFINAE to detect whether using operator<< would work.
 template <typename T, typename = void>
 struct SupportsOstreamOperator : std::false_type {};
@@ -102,29 +64,6 @@ struct SupportsOstreamOperator<T,
 
 }  // namespace internal
 
-// TODO(crbug.com/554293): Remove this when all platforms have this in the std
-// namespace.
-template <class Lvalue, class Rvalue>
-struct is_assignable : public internal::IsAssignableImpl<Lvalue, Rvalue> {};
-
-// is_copy_assignable is true if a T const& is assignable to a T&.
-// TODO(crbug.com/554293): Remove this when all platforms have this in the std
-// namespace.
-template <class T>
-struct is_copy_assignable
-    : public is_assignable<typename std::add_lvalue_reference<T>::type,
-                           typename std::add_lvalue_reference<
-                               typename std::add_const<T>::type>::type> {};
-
-// is_move_assignable is true if a T&& is assignable to a T&.
-// TODO(crbug.com/554293): Remove this when all platforms have this in the std
-// namespace.
-template <class T>
-struct is_move_assignable
-    : public is_assignable<typename std::add_lvalue_reference<T>::type,
-                           const typename std::add_rvalue_reference<T>::type> {
-};
-
 // underlying_type produces the integer type backing an enum type.
 // TODO(crbug.com/554293): Remove this when all platforms have this in the std
 // namespace.