Make callers of CommandLine use it via the base:: namespace.

content/browser/theme_helper_mac.mm

Index: content/browser/theme_helper_mac.mm
diff --git a/content/browser/theme_helper_mac.mm b/content/browser/theme_helper_mac.mm
index 9f0f86d1a59dd253b3f52cf74f66e3b391fef770..af3b428ef5a0d0f740942b8a6d7b59f816b91b76 100644
--- a/content/browser/theme_helper_mac.mm
+++ b/content/browser/theme_helper_mac.mm
@@ -53,7 +53,8 @@ suspensionBehavior:NSNotificationSuspensionBehaviorCoalesce];
   // In single-process mode, renderers will catch these notifications
   // themselves and listening for them here may trigger the DCHECK in Observe().
   if ([NSScroller respondsToSelector:@selector(preferredScrollerStyle)] &&
-      !CommandLine::ForCurrentProcess()->HasSwitch(switches::kSingleProcess)) {
+      !base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kSingleProcess)) {
     [[NSNotificationCenter defaultCenter]
         addObserver:self
            selector:@selector(behaviorPrefsChanged:)