Debug Info: move DIScope::getContext to DwarfDebug.

DIScope::getContext is a wrapper function that calls the specific getContext
method on each subclass. When we switch DIType::getContext to return DIScopeRef
instead of DIScope, DIScope::getContext can no longer return a DIScope without
a type identifier map.
    
DIScope::getContext is only used by DwarfDebug, so we move it to DwarfDebug
to have easy access to the type identifier map.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190330 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/DebugInfo.h

@@ -200,9 +200,6 @@ namespace llvm {
   public:
     explicit DIScope(const MDNode *N = 0) : DIDescriptor (N) {}
 
-    /// Gets the parent scope for this scope node or returns a
-    /// default constructed scope.
-    DIScope getContext() const;
     StringRef getFilename() const;
     StringRef getDirectory() const;