Warn user in case extension delays network traffic too much.

chrome/browser/resources/options/extension_settings.css

Index: chrome/browser/resources/options/extension_settings.css
diff --git a/chrome/browser/resources/options/extension_settings.css b/chrome/browser/resources/options/extension_settings.css
index 471d4814faad0bda0d0a6dc167f785fec814e7a8..f24a0053d9339a08b3e4265ac9bd5150fac6c85f 100644
--- a/chrome/browser/resources/options/extension_settings.css
+++ b/chrome/browser/resources/options/extension_settings.css
@@ -138,6 +138,22 @@ found in the LICENSE file.
   -webkit-user-select: none;
 }
 
+.extension-warnings-title {
+  color: red;
+}
+
+.extension-warnings {
+  margin-top: 6px;
+}
+
+.extension-warnings ul {
+  margin: 0;
+}
+
+.extension-warnings > * {
+  white-space: normal;
+}
+
 .informative-text {
   color: gray;
 }