Bug 227032. cleanup nsDownloadProxy a bit, mostly:

deal with prefs service or the pref not being there
use nsIPrefBranch for do_GetService instead of a separate QI

r=neil.parkwaycc.co.uk sr=darin

xpfe/components/download-manager/src/nsDownloadProxy.h

@@ -53,7 +53,7 @@ class nsDownloadProxy : public nsIDownload,
 public:
 
   nsDownloadProxy() { }
-  virtual ~nsDownloadProxy() { };
+  virtual ~nsDownloadProxy() { }
 
   NS_DECL_ISUPPORTS
 
@@ -65,26 +65,30 @@ public:
                      nsIWebBrowserPersist* aPersist) {
     nsresult rv;
     nsCOMPtr<nsIDownloadManager> dm = do_GetService("@mozilla.org/download-manager;1", &rv);
-    if (NS_FAILED(rv)) return rv;
+    if (NS_FAILED(rv))
+      return rv;
     
     rv = dm->AddDownload(aSource, aTarget, aDisplayName, aMIMEInfo, aStartTime, aPersist, getter_AddRefs(mInner));
-    if (NS_FAILED(rv)) return rv;
+    if (NS_FAILED(rv))
+      return rv;
 
-    PRInt32 behavior = 0;
-    nsCOMPtr<nsIPrefService> prefs = do_GetService("@mozilla.org/preferences-service;1", &rv);
-    if (NS_FAILED(rv)) return rv;
-    nsCOMPtr<nsIPrefBranch> branch = do_QueryInterface(prefs);
+    PRInt32 behavior;
+    nsCOMPtr<nsIPrefBranch> branch = do_GetService("@mozilla.org/preferences-service;1", &rv);
+    if (NS_SUCCEEDED(rv))
+      rv = branch->GetIntPref(DOWNLOAD_MANAGER_BEHAVIOR_PREF, &behavior);
+    if (NS_FAILED(rv))
+      behavior = 0;
 
-    branch->GetIntPref(DOWNLOAD_MANAGER_BEHAVIOR_PREF, &behavior);
     if (behavior == 0)
-      return dm->Open(nsnull, this);
-    if (behavior == 1) {
+      rv = dm->Open(nsnull, this);
+    else if (behavior == 1) {
       nsAutoString path;
       rv = aTarget->GetPath(path);
-      if (NS_FAILED(rv)) return rv;
+      if (NS_FAILED(rv))
+        return rv;
 
       NS_ConvertUCS2toUTF8 utf8Path(path);
-      return dm->OpenProgressDialogFor(utf8Path, nsnull, PR_TRUE);
+      rv = dm->OpenProgressDialogFor(utf8Path, nsnull, PR_TRUE);
     }
     return rv;
   }