[content shell] further restrict what files to open during layout tests

BUG=111316
R=marja@chromium.org

Review URL: https://codereview.chromium.org/15979019

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@203934 0039d316-1c4b-4281-b951-d872f2087c98

content/shell/shell_download_manager_delegate.cc

@@ -91,7 +91,8 @@ bool ShellDownloadManagerDelegate::ShouldOpenDownload(
       DownloadItem* item,
       const DownloadOpenDelayedCallback& callback) {
   if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kDumpRenderTree) &&
-      WebKitTestController::Get()->IsMainWindow(item->GetWebContents())) {
+      WebKitTestController::Get()->IsMainWindow(item->GetWebContents()) &&
+      item->GetMimeType() == "text/html") {
     WebKitTestController::Get()->OpenURL(
         net::FilePathToFileURL(item->GetFullPath()));
   }