[M74]: Check enabled_ before getting a SafeBrowsingApiHandler instance

R=drubery
TBR=vakh@chromium.org

(cherry picked from commit b11df6ef5e57d35cdf1707a30809e2d75613974a)

Bug: 940345,907280
Change-Id: I56bcae95a16e9b4235ac3b25986965ac764af009
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1516042
Auto-Submit: Varun Khaneja <vakh@chromium.org>
Reviewed-by: Daniel Rubery <drubery@chromium.org>
Commit-Queue: Daniel Rubery <drubery@chromium.org>
Commit-Queue: Varun Khaneja <vakh@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#639613}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1518448
Reviewed-by: Varun Khaneja <vakh@chromium.org>
Cr-Commit-Position: refs/branch-heads/3729@{#50}
Cr-Branched-From: d4a8972-refs/heads/master@{#638880}

Author: aawc

components/safe_browsing/android/remote_database_manager.cc

@@ -295,6 +295,10 @@ safe_browsing::ThreatSource RemoteSafeBrowsingDatabaseManager::GetThreatSource()
 }
 
 std::string RemoteSafeBrowsingDatabaseManager::GetSafetyNetId() const {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  if (!enabled_)
+    return std::string();
+
   SafeBrowsingApiHandler* api_handler = SafeBrowsingApiHandler::GetInstance();
   DCHECK(api_handler) << "SafeBrowsingApiHandler was never constructed";
   return api_handler->GetSafetyNetId();