[content shell] don't pop up a download dialog during layout tests

content/shell/shell_browser_context.cc

Index: content/shell/shell_browser_context.cc
diff --git a/content/shell/shell_browser_context.cc b/content/shell/shell_browser_context.cc
index 9eaa6b220d44593ce7023c6c75acd574af5479bc..86ae1a444b455cc1ccf871265b54b705b658e2b1 100644
--- a/content/shell/shell_browser_context.cc
+++ b/content/shell/shell_browser_context.cc
@@ -89,6 +89,11 @@ DownloadManagerDelegate* ShellBrowserContext::GetDownloadManagerDelegate()  {
   if (!download_manager_delegate_.get()) {
     download_manager_delegate_ = new ShellDownloadManagerDelegate();
     download_manager_delegate_->SetDownloadManager(manager);
+    CommandLine* cmd_line = CommandLine::ForCurrentProcess();
+    if (cmd_line->HasSwitch(switches::kDumpRenderTree)) {
+      download_manager_delegate_->SetDownloadBehaviorForTesting(
+          path_.Append(FILE_PATH_LITERAL("downloads")));
+    }
   }
 
   return download_manager_delegate_.get();