[sync] Check against nullptr web_data_backend->GetDatabase()

components/autofill/core/browser/webdata/autocomplete_sync_bridge.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/autofill/core/browser/webdata/autocomplete_sync_bridge.h"
 
 #include <algorithm>
 #include <set>
 #include <unordered_set>
 #include <utility>
@@ skipping 376 matching lines @@
       batch->Put(key, CreateEntityData(entry));
     }
   }
   callback.Run(std::move(batch));
 }
 
 void AutocompleteSyncBridge::GetAllData(DataCallback callback) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   std::vector<AutofillEntry> entries;
   if (!GetAutofillTable()->GetAllAutofillEntries(&entries)) {

[skym, 2017/05/08 22:22:12]

We're still going to crash if the user goes to chrome://sync-internals and the
db didn't init correctly, right?

[Patrick Noland, 2017/05/08 22:36:33]

When I tested this, sync-internals didn't crash. The Autofill type was reported
as "not running."

     change_processor()->ReportError(FROM_HERE,
                                     "Failed to load entries from table.");
     return;
   }
 
   auto batch = base::MakeUnique<MutableDataBatch>();
   for (const AutofillEntry& entry : entries) {
     batch->Put(GetStorageKeyFromModel(entry.key()), CreateEntityData(entry));
   }
   callback.Run(std::move(batch));
 }
 
 void AutocompleteSyncBridge::ActOnLocalChanges(

[skym, 2017/05/08 22:22:12]

Presumably this will never get called if the db is down? Have you tested?

[Patrick Noland, 2017/05/08 22:36:33]

When I tested, this was never called if the db was down. 

     const AutofillChangeList& changes) {
   if (!change_processor()->IsTrackingMetadata()) {
     return;
   }
 
   auto metadata_change_list =
       base::MakeUnique<syncer::SyncMetadataStoreChangeList>(GetAutofillTable(),
                                                             syncer::AUTOFILL);
   for (const auto& change : changes) {
     const std::string storage_key = GetStorageKeyFromModel(change.key());
@@ skipping 20 matching lines @@
         break;
       }
     }
   }
 
   if (Optional<ModelError> error = metadata_change_list->TakeError())
     change_processor()->ReportError(error.value());
 }
 
 void AutocompleteSyncBridge::LoadMetadata() {
   auto batch = base::MakeUnique<syncer::MetadataBatch>();

[skym, 2017/05/08 22:22:13]

Why make the batch first?

[Patrick Noland, 2017/05/08 22:36:33]

Done.

+  if (!web_data_backend_ || !web_data_backend_->GetDatabase() ||
+      !GetAutofillTable()) {
+    change_processor()->ReportError(FROM_HERE,
+                                    "Failed to load AutofillWebDatabase.");
+    return;
+  }
+
   if (!GetAutofillTable()->GetAllSyncMetadata(syncer::AUTOFILL, batch.get())) {
     change_processor()->ReportError(
         FROM_HERE, "Failed reading autofill metadata from WebDatabase.");
     return;
   }
   change_processor()->ModelReadyToSync(std::move(batch));
 }
 
 std::string AutocompleteSyncBridge::GetClientTag(
     const EntityData& entity_data) {
@@ skipping 20 matching lines @@
     const AutofillChangeList& changes) {
   DCHECK(thread_checker_.CalledOnValidThread());
   ActOnLocalChanges(changes);
 }
 
 AutofillTable* AutocompleteSyncBridge::GetAutofillTable() const {
   return AutofillTable::FromWebDatabase(web_data_backend_->GetDatabase());
 }
 
 }  // namespace autofill