Don't show FileManagerDialog if another FileManagerDialog is shown in the same tab.

chrome/browser/ui/views/file_manager_dialog_unittest.cc

Index: chrome/browser/ui/views/file_manager_dialog_unittest.cc
diff --git a/chrome/browser/ui/views/file_manager_dialog_unittest.cc b/chrome/browser/ui/views/file_manager_dialog_unittest.cc
index 33ad4f0aed2bfebbf88fcdfd93fbf3e3dd1cd9e2..122be1f5c97edb185fde5be4e6ae22c86dd375cd 100644
--- a/chrome/browser/ui/views/file_manager_dialog_unittest.cc
+++ b/chrome/browser/ui/views/file_manager_dialog_unittest.cc
@@ -13,7 +13,9 @@ class FileManagerDialogTest : public testing::Test {
                                          int32 tab_id) {
     FileManagerDialog* dialog = new FileManagerDialog(listener);
     // Simulate the dialog opening.
+    EXPECT_FALSE(FileManagerDialog::PendingExists(tab_id));
     dialog->AddPending(tab_id);
+    EXPECT_TRUE(FileManagerDialog::PendingExists(tab_id));
     return dialog;
   }
 };