De-ASTContext-ify DeclContext.

Remove ASTContext parameter from DeclContext's methods. This change cascaded down to other Decl's methods and changes to call sites started "escalating".
Timings using pre-tokenized "cocoa.h" showed only a ~1% increase in time run between and after this commit.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@74506 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaExprCXX.cpp b/lib/Sema/SemaExprCXX.cpp
index 0efd8ff..7afa594 100644
--- a/lib/Sema/SemaExprCXX.cpp
+++ b/lib/Sema/SemaExprCXX.cpp
@@ -552,7 +552,7 @@
                                   bool AllowMissing, FunctionDecl *&Operator)
 {
   DeclContext::lookup_iterator Alloc, AllocEnd;
-  llvm::tie(Alloc, AllocEnd) = Ctx->lookup(Context, Name);
+  llvm::tie(Alloc, AllocEnd) = Ctx->lookup(Name);
   if (Alloc == AllocEnd) {
     if (AllowMissing)
       return false;
@@ -657,7 +657,7 @@
   // Check if this function is already declared.
   {
     DeclContext::lookup_iterator Alloc, AllocEnd;
-    for (llvm::tie(Alloc, AllocEnd) = GlobalCtx->lookup(Context, Name);
+    for (llvm::tie(Alloc, AllocEnd) = GlobalCtx->lookup(Name);
          Alloc != AllocEnd; ++Alloc) {
       // FIXME: Do we need to check for default arguments here?
       FunctionDecl *Func = cast<FunctionDecl>(*Alloc);
@@ -680,7 +680,7 @@
   // FIXME: Also add this declaration to the IdentifierResolver, but
   // make sure it is at the end of the chain to coincide with the
   // global scope.
-  ((DeclContext *)TUScope->getEntity())->addDecl(Context, Alloc);
+  ((DeclContext *)TUScope->getEntity())->addDecl(Alloc);
 }
 
 /// ActOnCXXDelete - Parsed a C++ 'delete' expression (C++ 5.3.5), as in: