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/Analysis/RegionStore.cpp b/lib/Analysis/RegionStore.cpp
index 493f14d..e937757 100644
--- a/lib/Analysis/RegionStore.cpp
+++ b/lib/Analysis/RegionStore.cpp
@@ -1018,8 +1018,7 @@
 
   // FIXME: We shouldn't use a std::vector.  If RecordDecl doesn't have a
   // reverse iterator, we should implement one.
-  std::vector<FieldDecl *> Fields(RD->field_begin(getContext()), 
-                                  RD->field_end(getContext()));
+  std::vector<FieldDecl *> Fields(RD->field_begin(), RD->field_end());
 
   for (std::vector<FieldDecl *>::reverse_iterator Field = Fields.rbegin(),
                                                FieldEnd = Fields.rend();
@@ -1207,8 +1206,7 @@
 
   RecordDecl::field_iterator FI, FE;
 
-  for (FI = RD->field_begin(getContext()), FE = RD->field_end(getContext());
-       FI != FE; ++FI, ++VI) {
+  for (FI = RD->field_begin(), FE = RD->field_end(); FI != FE; ++FI, ++VI) {
 
     if (VI == VE)
       break;