Update QR Code scanner caption string and padding.

ios/chrome/browser/ui/qr_scanner/qr_scanner_view.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/browser/ui/qr_scanner/qr_scanner_view.h"
 
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_nsobject.h"
 #include "ios/chrome/browser/ui/icons/chrome_icon.h"
@@ skipping 23 matching lines @@
 const CGFloat kViewportBorderCornerRadius = 2.0;
 // Line width of the viewport border.
 const CGFloat kViewportBorderLineWidth = 4.0;
 // Shadow opacity of the viewport border.
 const CGFloat kViewportBorderShadowOpacity = 1.0;
 // Shadow radius of the viewport border.
 const CGFloat kViewportBorderShadowRadius = 10.0;
 // Padding of the viewport caption, below the viewport.
 const CGFloat kViewportCaptionVerticalPadding = 14.0;
 // Padding of the viewport caption from the edges of the superview.
-const CGFloat kViewportCaptionHorizontalPadding = 20.0;
+const CGFloat kViewportCaptionHorizontalPadding = 31.0;
 // Shadow opacity of the viewport caption.
 const CGFloat kViewportCaptionShadowOpacity = 1.0;
 // Shadow radius of the viewport caption.
 const CGFloat kViewportCaptionShadowRadius = 5.0;
 
 // Duration of the flash animation played when a code is scanned.
 const CGFloat kFlashDuration = 0.5;
 
 // Returns a square of size |rectSize| centered inside |frameSize|.
 CGRect CenteredRectForViewport(CGSize frameSize, CGFloat rectSize) {
@@ skipping 484 matching lines @@
   [NSLayoutConstraint activateConstraints:@[
     [[_previewOverlay centerXAnchor]
         constraintEqualToAnchor:[self centerXAnchor]],
     [[_previewOverlay centerYAnchor]
         constraintEqualToAnchor:[self centerYAnchor]],
     _overlaySquareConstraint, _overlayWidthConstraint, _overlayHeightConstraint
   ]];
 }
 
 @end