Removed implementation of application:performFetchWithCompletionHandler:

Without specifying "fetch" in Info.plist, runtime generates spurious
warning messages.

Bug: 795802
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: Ie9e73e52d626a170645a98db8e7ae90b61755ce1
Reviewed-on: https://chromium-review.googlesource.com/1050687Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Commit-Queue: Peter Lee <pkl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557868}

ios/chrome/app/main_application_delegate.mm

@@ -155,25 +155,6 @@
 
 #pragma mark Downloading Data in the Background
 
-- (void)application:(UIApplication*)application
-    performFetchWithCompletionHandler:
-        (void (^)(UIBackgroundFetchResult))completionHandler {
-  if ([_appState isInSafeMode])
-    return;
-
-  if ([application applicationState] != UIApplicationStateBackground) {
-    // If this handler is called in foreground, it means it has to be activated.
-    // Returning |UIBackgroundFetchResultNewData| means that the handler will be
-    // called again in case of a crash.
-    completionHandler(UIBackgroundFetchResultNewData);
-    return;
-  }
-  // This initialization to BACKGROUND stage may not be necessary, but is
-  // preserved in case somewhere there is a dependency on this.
-  [_browserLauncher startUpBrowserToStage:INITIALIZATION_STAGE_BACKGROUND];
-  completionHandler(UIBackgroundFetchResultFailed);
-}
-
 - (void)application:(UIApplication*)application
     handleEventsForBackgroundURLSession:(NSString*)identifier
                       completionHandler:(void (^)(void))completionHandler {