Revert "Reland "Enable sync trusted vault support by default""

This reverts commit be06dabb.

Reason for revert: the feature is not ready yet.

Original change's description:
> Reland "Enable sync trusted vault support by default"
> 
> This is a reland of f52179a5
> 
> The feature was disabled by default before branching because some
> implementation parts were missing on Android.
> 
> Original change's description:
> > Enable sync trusted vault support by default
> >
> > The feature is in a working state can be enabled by default.
> >
> > Bug: 1000146
> > Change-Id: I66ef6f65d97234f47eaa76d1daafb8d3637692ed
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2000702
> > Reviewed-by: Marc Treib <treib@chromium.org>
> > Commit-Queue: Mikel Astiz <mastiz@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#731898}
> 
> Bug: 1000146
> Change-Id: If2c11c87bbc021daaa6656f9e85b592302dd8327
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2035966
> Reviewed-by: Marc Treib <treib@chromium.org>
> Commit-Queue: Mikel Astiz <mastiz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#738548}

TBR=treib@chromium.org,mastiz@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1000146
Change-Id: I44607cf1822145fb8a98e4a72a1361dbae274b00
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2127091
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#755994}

components/sync/engine/sync_engine_switches.cc

@@ -26,7 +26,7 @@ const base::Feature kSyncUseScryptForNewCustomPassphrases{
     "SyncUseScryptForNewCustomPassphrases", base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kSyncSupportTrustedVaultPassphrase{
-    "SyncSupportTrustedVaultPassphrase", base::FEATURE_ENABLED_BY_DEFAULT};
+    "SyncSupportTrustedVaultPassphrase", base::FEATURE_DISABLED_BY_DEFAULT};
 
 // If enabled sync cycle ends by collecting contributions from all datatypes
 // and having less than max_commit_batch_size() entries to commit. If disabled

components/sync/nigori/nigori_sync_bridge_impl_unittest.cc

@@ -1615,6 +1615,10 @@ TEST_F(NigoriSyncBridgeImplTest,
 // custom passphrase. The bridge should report model error.
 TEST(NigoriSyncBridgeImplPersistenceTest,
      ShouldFailOnInvalidRemoteTransitionFromTrustedVaultAfterRestart) {
+  base::test::ScopedFeatureList override_features;
+  override_features.InitAndEnableFeature(
+      switches::kSyncSupportTrustedVaultPassphrase);
+
   // Emulate storing on disc.
   auto storage1 = std::make_unique<testing::NiceMock<MockNigoriStorage>>();
   sync_pb::NigoriLocalData nigori_local_data;