In case of an error in AutofillCounter's queries, do not crash.

Before OnWebDataServiceRequestDone is called for a request, the request is marked as being complete by being removed from the WebDataRequestManager's pending_requests_ map.

When a query from AutofillCounter fails, it is handled inside OnWebDataServiceRequestDone. By that time, it has been removed from the pending_requests_ map and is no longer allowed to be canceled. Therefore, make sure that AutofillCounter marks it as being complete so that it doesn't try to cancel it.

BUG=672823

Review-Url: https://codereview.chromium.org/2555373007
Cr-Commit-Position: refs/heads/master@{#437885}

components/browsing_data/core/counters/autofill_counter.cc

@@ -81,7 +81,20 @@ void AutofillCounter::OnWebDataServiceRequestDone(
     WebDataServiceBase::Handle handle,
     std::unique_ptr<WDTypedResult> result) {
   DCHECK(thread_checker_.CalledOnValidThread());
+
   if (!result) {
+    // CancelAllRequests will cancel all queries that are active; the query that
+    // just failed is complete and cannot be canceled so zero it out.
+    if (handle == suggestions_query_) {
+      suggestions_query_ = 0;
+    } else if (handle == credit_cards_query_) {
+      credit_cards_query_ = 0;
+    } else if (handle == addresses_query_) {
+      addresses_query_ = 0;
+    } else {
+      NOTREACHED();
+    }
+
     CancelAllRequests();
     return;
   }