bug 100132: clean up over-zealous error masking in

nsRDFXMLDataSource::BlockingParse(), and bring nsLocalFileUnix's
OpenNSPRFileDesc() return values in line with other platforms.
r=waterson, sr=brendan

rdf/base/src/nsRDFXMLDataSource.cpp

@@ -560,8 +560,9 @@ RDFXMLDataSourceImpl::BlockingParse(nsIURI* aURL, nsIStreamListener* aConsumer)
     PRUint32 sourceOffset = 0;
     rv = channel->Open(&in);
 
-    // If we couldn't open the channel, then just return.
+    // Report success if the file doesn't exist, but propagate other errors.
-    if (NS_FAILED(rv)) return NS_OK;
+    if (rv == NS_ERROR_FILE_NOT_FOUND) return NS_OK;
+    if (NS_FAILED(rv)) return rv;
 
     NS_ASSERTION(in != nsnull, "no input stream");
     if (! in) return NS_ERROR_FAILURE;

xpcom/io/nsLocalFileUnix.cpp

@@ -350,7 +350,7 @@ nsLocalFile::OpenNSPRFileDesc(PRInt32 flags, PRInt32 mode, PRFileDesc **_retval)
 
     *_retval = PR_Open(mPath.get(), flags, mode);
     if (! *_retval)
-        return NS_ERROR_FAILURE;
+        return NS_ErrorAccordingToNSPR();
 
     return NS_OK;
 }