Don't rely on headers including stuff: be sure to include nsIRDFResource.h and nsIRDFService.h.

mailnews/base/src/nsMsgFolderDataSource.h

@@ -17,6 +17,7 @@
  */
 
 #include "nsIRDFDataSource.h"
+#include "nsIRDFService.h"
 
 #include "nsIFolderListener.h"
 

mailnews/base/src/nsMsgMessageDataSource.h

@@ -17,6 +17,7 @@
  */
 
 #include "nsIRDFDataSource.h"
+#include "nsIRDFService.h"
 #include "nsIMsgHeaderParser.h"
 
 /**

mailnews/base/src/nsMsgRDFDataSource.h

@@ -21,6 +21,7 @@
 #define __nsMsgRDFDataSource_h
 
 #include "nsIRDFDataSource.h"
+#include "nsIRDFService.h"
 #include "nsIServiceManager.h"
 #include "nsVoidArray.h"
 

mailnews/base/src/nsMsgRDFUtils.h

@@ -19,6 +19,7 @@
 //This file holds some useful utility functions and declarations used by our datasources.
 
 #include "rdf.h"
+#include "nsIRDFResource.h"
 #include "nsIRDFNode.h"
 #include "nsString.h"