Remove fixme, use ASTContext::getCanonicalTemplateSpecializationType

[v.g.vassilev]

Landed in r291552.

lib/Sema/SemaTemplate.cpp

if (CanonType.isNull())
                TemplateArgs, InstantiationDependent)) {
     // This class template specialization is a dependent
     // type. Therefore, its canonical type is another class template
     // specialization type that contains all of the converted
     // arguments in canonical form. This ensures that, e.g., A<T> and
     // A<T, T> have identical types when A is declared as:
     //
     //   template<typename T, typename U = T> struct A;
-    TemplateName CanonName = Context.getCanonicalTemplateName(Name);
-    CanonType = Context.getTemplateSpecializationType(CanonName,
-                                                      Converted);
-
-    // FIXME: CanonType is not actually the canonical type, and unfortunately
-    // it is a TemplateSpecializationType that we will never use again.
-    // In the future, we need to teach getTemplateSpecializationType to only
-    // build the canonical type and return that to us.
-    CanonType = Context.getCanonicalType(CanonType);
+    CanonType = Context.getCanonicalTemplateSpecializationType(Name, Converted);
 
     // This might work out to be a current instantiation, in which
     // case the canonical type needs to be the InjectedClassNameType.
     //
     // TODO: in theory this could be a simple hashtable lookup; most
     // changes to CurContext don't change the set of current
     // instantiations.
     if (isa<ClassTemplateDecl>(Template)) {

 /// parameters that precede \p Param in the template parameter list.
 /// \returns the substituted template argument, or NULL if an error occurred.
 static TypeSourceInfo *
 SubstDefaultTemplateArgument(Sema &SemaRef,
                              TemplateDecl *Template,
                              SourceLocation TemplateLoc,
                              SourceLocation RAngleLoc,
                              TemplateTypeParmDecl *Param,
                              SmallVectorImpl<TemplateArgument> &Converted) {
   TypeSourceInfo *ArgType = Param->getDefaultArgumentInfo();
 
   // If the argument type is dependent, instantiate it now based
   // on the previously-computed template arguments.
   if (ArgType->getType()->isDependentType()) {
     Sema::InstantiatingTemplate Inst(SemaRef, TemplateLoc,
                                      Param, Template, Converted,
                                      SourceRange(TemplateLoc, RAngleLoc));