Revert "Prevent deadlock by checking kRestrictGoogleWebVisibility sooner."

This reverts commit b622082c.

Reason for revert: The CL seems to cause flakiness of
VariationsHttpHeadersBrowserTestWithRestrictedVisibility.TestRestrictGoogleWebVisibilityInThirdPartyContexts, crbug.com/1133291

Original change's description:
> Prevent deadlock by checking kRestrictGoogleWebVisibility sooner.
>
> More specifically, check the feature's state after field trials have
> been created from the variations seed and before the variations
> header is updated.
>
> Checking the state for the first time in
> VariationsIdsProvider::GenerateBase64EncodedProto() could cause a
> deadlock.
>
> Bug: 1094303
> Change-Id: I53fe3446e3a4567d4b9122b54642b5744eb8b46e
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2431556
> Commit-Queue: Caitlin Fischer <caitlinfischer@google.com>
> Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
> Reviewed-by: Jesse Doherty <jwd@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#811566}

TBR=jwd@chromium.org,asvitkine@chromium.org,caitlinfischer@google.com

Change-Id: I8cbc093f9bd9d978a13eb881d7dc319309a808fe
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1094303, 1133291
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2438057Reviewed-by: Christoph Schwering <schwering@google.com>
Commit-Queue: Christoph Schwering <schwering@google.com>
Cr-Commit-Position: refs/heads/master@{#811654}

components/variations/net/variations_http_headers.cc

@@ -196,8 +196,7 @@ variations::mojom::GoogleWebVisibility GetVisibilityKey(
     const network::ResourceRequest& resource_request) {
   bool use_first_party_visibility =
       IsFirstPartyContext(owner, resource_request) &&
-      VariationsIdsProvider::GetInstance()
-          ->IsRestrictGoogleWebVisibilityEnabled();
+      base::FeatureList::IsEnabled(internal::kRestrictGoogleWebVisibility);
 
   return use_first_party_visibility
              ? variations::mojom::GoogleWebVisibility::FIRST_PARTY

components/variations/variations_ids_provider.cc

@@ -215,13 +215,8 @@ void VariationsIdsProvider::InitVariationIDsCacheIfNeeded() {
   if (variation_ids_cache_initialized_)
     return;
 
-  // Must be done before AddObserver() to avoid deadlock in
-  // OnFieldTrialGroupFinalized().
-  is_restrict_google_web_visibility_enabled_ =
-      base::FeatureList::IsEnabled(internal::kRestrictGoogleWebVisibility);
-
-  // Register for additional cache updates. This is done before initializing the
-  // cache to avoid a race that could cause registered FieldTrials to be missed.
+  // Register for additional cache updates. This is done first to avoid a race
+  // that could cause registered FieldTrials to be missed.
   bool success = base::FieldTrialList::AddObserver(this);
   DCHECK(success);
 
@@ -295,7 +290,8 @@ std::string VariationsIdsProvider::GenerateBase64EncodedProto(
         proto.add_variation_id(entry.first);
         break;
       case GOOGLE_WEB_PROPERTIES_FIRST_PARTY:
-        if (IsRestrictGoogleWebVisibilityEnabled()) {
+        if (base::FeatureList::IsEnabled(
+                internal::kRestrictGoogleWebVisibility)) {
           if (is_first_party_context)
             proto.add_variation_id(entry.first);
         } else {
@@ -309,7 +305,8 @@ std::string VariationsIdsProvider::GenerateBase64EncodedProto(
         proto.add_trigger_variation_id(entry.first);
         break;
       case GOOGLE_WEB_PROPERTIES_TRIGGER_FIRST_PARTY:
-        if (IsRestrictGoogleWebVisibilityEnabled()) {
+        if (base::FeatureList::IsEnabled(
+                internal::kRestrictGoogleWebVisibility)) {
           if (is_first_party_context)
             proto.add_trigger_variation_id(entry.first);
         } else {

components/variations/variations_ids_provider.h

@@ -126,12 +126,6 @@ class VariationsIdsProvider : public base::FieldTrialList::Observer,
   // Resets any cached state for tests.
   void ResetForTesting();
 
-  // Returns true if kRestrictGoogleWebVisibility is enabled and false
-  // otherwise.
-  bool IsRestrictGoogleWebVisibilityEnabled() {
-    return is_restrict_google_web_visibility_enabled_;
-  }
-
  private:
   friend struct base::DefaultSingletonTraits<VariationsIdsProvider>;
 
@@ -227,9 +221,6 @@ class VariationsIdsProvider : public base::FieldTrialList::Observer,
   // Whether or not we've initialized the caches.
   bool variation_ids_cache_initialized_;
 
-  // Denotes whether kRestrictGoogleWebVisibility is enabled.
-  bool is_restrict_google_web_visibility_enabled_ = false;
-
   // Keep a cache of variation IDs that are transmitted in headers to Google.
   // This consists of a list of valid IDs, and the actual transmitted header.
   std::set<VariationIDEntry> variation_ids_set_;