Bug 183871

Crash on "Show hidden files and directories" [@ nsFileView::SetDirectory(nsIFile*) ]
fix: don't let files be initialized with relative paths.
also fix the directory service to not do that.

r=dougt sr=bzbarsky

xpcom/io/nsLocalFileUnix.cpp

@@ -270,6 +270,9 @@ nsLocalFile::InitWithNativePath(const nsACString &filePath)
         }
         
         mPath = homePath + Substring(filePath, 1, filePath.Length() - 1);
+    } else if (filePath.IsEmpty() || filePath.First() != '/') {
+      NS_ERROR("Relative paths not allowed");
+      return NS_ERROR_FILE_UNRECOGNIZED_PATH;
     } else {
         mPath = filePath;
     }