Revert of Disable PluginPowerSaverBrowserTest.BackgroundTabPlugins

chrome/browser/plugins/plugin_power_saver_browsertest.cc

Index: chrome/browser/plugins/plugin_power_saver_browsertest.cc
diff --git a/chrome/browser/plugins/plugin_power_saver_browsertest.cc b/chrome/browser/plugins/plugin_power_saver_browsertest.cc
index f00200870abb1168a3e43b1b25b711be17cf9d4a..2b33c53673efcf3085aac40b94a5d25bcdd22c68 100644
--- a/chrome/browser/plugins/plugin_power_saver_browsertest.cc
+++ b/chrome/browser/plugins/plugin_power_saver_browsertest.cc
@@ -657,9 +657,7 @@
   VerifyPluginMarkedEssential(GetActiveWebContents(), "plugin");
 }
 
-// Flaky on all bots. crbug.com/665706
-IN_PROC_BROWSER_TEST_F(PluginPowerSaverBrowserTest,
-                       DISABLED_BackgroundTabPlugins) {
+IN_PROC_BROWSER_TEST_F(PluginPowerSaverBrowserTest, BackgroundTabPlugins) {
   content::WebContents* background_contents = LoadHTMLInBackgroundTab(
       "<object id='same_origin' data='fake.swf' "
       "    type='application/x-shockwave-flash'></object>"