[iOS] Hide status bar during launch.

The system truncates the middle of the launch screen if content is
centered on it and the status bar is visible. Hide the status bar while
the launch screen is displayed in order to prevent this distortion. After the
application launches, the status bar visibility will be based on the values
returned from |prefersStatusBarHidden| methods.

Bug: 784130
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I1ec35a8cf657e9eceb179b8f9da433fedc20161d
Reviewed-on: https://chromium-review.googlesource.com/1005782Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549947}

ios/chrome/app/resources/Info.plist

@@ -126,6 +126,8 @@
 	<true/>
 	<key>UIStatusBarStyle</key>
 	<string>UIStatusBarStyleLightContent</string>
+	<key>UIStatusBarHidden</key>
+	<true/>
 	<key>UISupportedInterfaceOrientations</key>
 	<array>
 		<string>UIInterfaceOrientationPortrait</string>