Use a test BrowserContext in DownloadItemImpl unittests.

content/browser/download/download_item_impl.cc

Index: content/browser/download/download_item_impl.cc
diff --git a/content/browser/download/download_item_impl.cc b/content/browser/download/download_item_impl.cc
index 0dd72a208e0519724a8092ed27e60b7473f6c22d..a5dfaec1af2ac84f009d4745667178900c7bb220 100644
--- a/content/browser/download/download_item_impl.cc
+++ b/content/browser/download/download_item_impl.cc
@@ -1698,12 +1698,10 @@ void DownloadItemImpl::ResumeInterruptedDownload() {
   if (GetWebContents()) {
     download_params = DownloadUrlParameters::FromWebContents(GetWebContents(),
                                                              GetOriginalUrl());
-  } else if (GetBrowserContext()) {
+  } else {
     download_params = make_scoped_ptr(
         new DownloadUrlParameters(GetOriginalUrl(), -1, -1, -1,
                                   GetBrowserContext()->GetResourceContext()));
-  } else {
-    return;
   }
 
   download_params->set_file_path(GetFullPath());