Fix feature flag experiment name.

The group name used in the variations' field trial test configuration
didn't match the one set in the flags configuration, causing DCHECK
crashes when the feature flag is used. This change makes those names
match.

Bug: 852872
Change-Id: Ie817d84bdf3801d344497543b21a12428dc66fbf
Reviewed-on: https://chromium-review.googlesource.com/c/1257653Reviewed-by: Dan H <harringtond@google.com>
Commit-Queue: Carlos Knippschild <carlosk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#596370}

chrome/browser/about_flags.cc

@@ -3679,7 +3679,7 @@ const FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kNewNetErrorPageUIDescription, kOsAndroid,
      FEATURE_WITH_PARAMS_VALUE_TYPE(features::kNewNetErrorPageUI,
                                     kNewNetErrorPageUIVariations,
-                                    "NewNetErrorPageUI")},
+                                    "OfflineContentOnDinoPage")},
 #endif  // defined(OS_ANDROID)
 
 #if defined(OS_ANDROID)