Allow for pausing background tabs on desktop via about:flags.

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 495a80a66b444b4796c3958ec8e4e6af84523c1b..93331d084bf67b74c34cee6d93fa114798a23016 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -2572,6 +2572,13 @@ const FeatureEntry kFeatureEntries[] = {
      FEATURE_VALUE_TYPE(chrome::android::kCustomContextMenu)},
 #endif  // OS_ANDROID
 
+#if defined(OS_CHROMEOS) || defined(OS_LINUX) || defined(OS_MACOSX) || \
+    defined(OS_WIN)
+    {"pause-background-tabs", flag_descriptions::kPauseBackgroundTabsName,
+     flag_descriptions::kPauseBackgroundTabsDescription, kOsDesktop,
+     SINGLE_VALUE_TYPE(switches::kPauseBackgroundTabs)},
+#endif
+
     // NOTE: Adding new command-line switches requires adding corresponding
     // entries to enum "LoginCustomFlags" in histograms.xml. See note in
     // histograms.xml and don't forget to run AboutFlagsHistogramTest unit test.