Clean up some code related to field trial observing.

Removes a method declaration that no longer exists and fixes
a comment reference.

Bug: None
Change-Id: Ic80f0c0acc391d0eb4d9dd5459054a438d282327
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2013891
Auto-Submit: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Charlie Reis <creis@chromium.org>
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#734103}

components/variations/child_process_field_trial_syncer_unittest.cc

@@ -26,7 +26,7 @@ class TestFieldTrialObserver : public base::FieldTrialList::Observer {
   TestFieldTrialObserver() {}
   ~TestFieldTrialObserver() override { ClearCrashKeysInstanceForTesting(); }
 
-  // base::FieldTrial::Observer:
+  // base::FieldTrialList::Observer:
   void OnFieldTrialGroupFinalized(const std::string& trial_name,
                                   const std::string& group_name) override {
     observed_entries_.push_back(std::make_pair(trial_name, group_name));

content/browser/gpu/gpu_process_host.h

@@ -171,9 +171,6 @@ class GpuProcessHost : public BrowserChildProcessHostDelegate,
   void SendGpuProcessMessage(IPC::Message* message) override;
 #endif
 
-  // Message handlers.
-  void OnFieldTrialActivated(const std::string& trial_name);
-
   bool LaunchGpuProcess();
 
   void SendOutstandingReplies();