Navi: Use a different synthetic trial name than the study.

Bug: 919140
Change-Id: Ifc5c680e5e48afd4b0f75d260cd6c277350d5d7b
Reviewed-on: https://chromium-review.googlesource.com/c/1396712Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Hector Carmona <hcarmona@chromium.org>
Cr-Commit-Position: refs/heads/master@{#620107}

chrome/browser/ui/webui/welcome/nux_helper.cc

@@ -67,7 +67,7 @@ bool IsNuxOnboardingEnabled(Profile* profile) {
     // User will be tied to their original onboarding group, even after
     // experiment ends.
     ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial(
-        kNuxOnboardingStudyName, onboard_group);
+        "NaviOnboardingSynthetic", onboard_group);
 
     return base::FeatureList::IsEnabled(nux::kNuxOnboardingFeature);
 #else