Fix mime-type for filesystem: directory listings.

Bug: 937069
Change-Id: Ic00c4ea761b16c685ca200df03e0c856765d450f
Reviewed-on: https://chromium-review.googlesource.com/c/1496276
Reviewed-by: Robbie McElrath <rmcelrath@chromium.org>
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636671}
diff --git a/content/browser/fileapi/file_system_url_loader_factory.cc b/content/browser/fileapi/file_system_url_loader_factory.cc
index 115f82f..55e9a9a 100644
--- a/content/browser/fileapi/file_system_url_loader_factory.cc
+++ b/content/browser/fileapi/file_system_url_loader_factory.cc
@@ -348,7 +348,7 @@
     }
 
     network::ResourceResponseHead head;
-    head.mime_type = "text/plain";
+    head.mime_type = "text/html";
     head.charset = "utf-8";
     head.content_length = data_.size();
     head.headers = CreateHttpResponseHeaders(200);