[Files ranking] Fix bug: zero state result persist to search

There is a bug in the provider for zero state Drive file results that
means it returns results even when a search query is issued, messing
up the results for a search. This is caused by the result cache being
cleared at the wrong time.

Bug: 1022150
Change-Id: Ic1382e37a7991284c492963c57681d63f2f02a35
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1902167Reviewed-by: Thanh Nguyen <thanhdng@chromium.org>
Reviewed-by: Jia Meng <jiameng@chromium.org>
Commit-Queue: Tony Yeoman <tby@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713233}

chrome/browser/ui/app_list/search/drive_quick_access_provider.cc

@@ -94,6 +94,7 @@ DriveQuickAccessProvider::~DriveQuickAccessProvider() = default;
 
 void DriveQuickAccessProvider::Start(const base::string16& query) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  ClearResultsSilently();
   if (!query.empty())
     return;
 
@@ -102,7 +103,6 @@ void DriveQuickAccessProvider::Start(const base::string16& query) {
       "Apps.AppList.DriveQuickAccessProvider.TimeFromFetchToZeroStateStart",
       base::TimeTicks::Now() - latest_fetch_start_time_);
 
-  ClearResultsSilently();
   // Results are launched via DriveFS, so DriveFS must be mounted.
   bool drive_fs_mounted = drive_service_ && drive_service_->IsMounted();
   LogDriveFSMounted(drive_fs_mounted);