[Sync] Fix model_type_state if cache guid mismatches

In case when cache GUID mismatches the model_type_state must be dropped
and created again. In other case ModelTypeProcessor will be in invalid
state when it dropped all metadata but initial_sync_done is still true.

Bug: 947044
Change-Id: I7ed96cac1e326c3e2568e051576ac3964b659e9a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2100812
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Commit-Queue: Rushan Suleymanov <rushans@google.com>
Cr-Commit-Position: refs/heads/master@{#749791}

components/sync/model_impl/client_tag_based_model_type_processor.cc

@@ -147,12 +147,15 @@ void ClientTagBasedModelTypeProcessor::ConnectIfReady() {
                                 ModelTypeHistogramValue(type_));
     }
     ClearMetadataAndResetState();
+    model_type_state = entity_tracker_->model_type_state();
 
     // The model is still ready to sync (with the same |bridge_|) - replay
     // the initialization.
     model_ready_to_sync_ = true;
     // Notify the bridge sync is starting to simulate an enable event.
     bridge_->OnSyncStarting(activation_request_);
+
+    DCHECK(!model_type_state.initial_sync_done());
   }
 
   // Cache GUID verification earlier above guarantees the user is the same.

components/sync/model_impl/client_tag_based_model_type_processor_unittest.cc

@@ -2305,6 +2305,7 @@ TEST_F(ClientTagBasedModelTypeProcessorTest,
   EXPECT_NE(nullptr, worker());
   // Upon a mismatch, metadata should have been cleared.
   EXPECT_EQ(0U, db()->metadata_count());
+  EXPECT_FALSE(type_processor()->IsTrackingMetadata());
 }
 
 TEST_F(ClientTagBasedModelTypeProcessorTest,