changes microsummary load timeout from 10 seconds to 300 seconds (five minutes), which is long enough to handle almost every page load while still being short enough to cancel loads before they start to pile up

bug=347097
r=mconnor

browser/components/microsummaries/src/nsMicrosummaryService.js

@@ -2131,8 +2131,9 @@ MicrosummaryResource.prototype = {
     };
 
     // cancel loads that take too long
-    // timeout specified in seconds at browser.microsummary.requestTimeout, or 10 seconds
-    var timeout = getPref("browser.microsummary.requestTimeout", 10) * 1000;
+    // timeout specified in seconds at browser.microsummary.requestTimeout,
+    // or 300 seconds (five minutes)
+    var timeout = getPref("browser.microsummary.requestTimeout", 300) * 1000;
     var timerObserver = {
       _self: this,
       observe: function MSR_timerObserver_observe() {