chrome_features: Swap default mode for Usbguard feature flag.

This feature flag is being used as a kill switch and default enabled
is needed for this functionality.

BUG=chromium:870769
Signed-off-by: Allen Webb <allenwebb@google.com>
Change-Id: Ie48ad82a261ce996a908852ac82a6a886807b857
Reviewed-on: https://chromium-review.googlesource.com/1176475Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583480}

chrome/common/chrome_features.cc

@@ -660,7 +660,8 @@ const base::Feature kMachineLearningService{"MachineLearningService",
                                             base::FEATURE_DISABLED_BY_DEFAULT};
 
 // Enable USBGuard at the lockscreen on Chrome OS.
-const base::Feature kUsbguard{"USBGuard", base::FEATURE_DISABLED_BY_DEFAULT};
+// TODO(crbug.com/874630): Remove this kill-switch
+const base::Feature kUsbguard{"USBGuard", base::FEATURE_ENABLED_BY_DEFAULT};
 #endif  // defined(OS_CHROMEOS)
 
 #if !defined(OS_ANDROID)