[tab_grid] Hack-in new tab FAB action.

ios/clean/chrome/browser/ui/tab_grid/mdc_floating_button+cr_tab_grid.mm

 // Copyright 2017 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/clean/chrome/browser/ui/tab_grid/mdc_floating_button+cr_tab_grid.h"
 
 #import "ios/chrome/browser/ui/colors/MDCPalette+CrAdditions.h"
 #include "ios/chrome/browser/ui/rtl_geometry.h"
 #include "ios/chrome/grit/ios_strings.h"
+#import "ios/clean/chrome/browser/ui/actions/tab_grid_actions.h"
 #import "ios/third_party/material_components_ios/src/components/Palettes/src/MaterialPalettes.h"
 #include "ui/base/l10n/l10n_util.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 namespace {
 // Margin from trailing and bottom edges.
 const CGFloat kNewTabButtonMarginFromEdges = 48;
@@ skipping 15 matching lines @@
     [button setAutoresizingMask:UIViewAutoresizingFlexibleTopMargin |
                                 UIViewAutoresizingFlexibleLeadingMargin()];
 
     MDCPalette* palette = [MDCPalette cr_bluePalette];
     [button setInkColor:[[palette tint300] colorWithAlphaComponent:0.5f]];
     [button setBackgroundColor:[palette tint500] forState:UIControlStateNormal];
     [button setBackgroundColor:[UIColor colorWithWhite:0.8f alpha:1.0f]
                       forState:UIControlStateDisabled];
     [button setAccessibilityLabel:l10n_util::GetNSString(
                                       IDS_IOS_TAB_SWITCHER_CREATE_NEW_TAB)];
+    [button addTarget:nil
+                  action:@selector(createNewTab:)
+        forControlEvents:UIControlEventTouchUpInside];
   }
   return button;
 }
 
 + (CGRect)cr_frameForTabGridNewTabButtonInRect:(CGRect)rect {
   CGFloat yOrigin = CGRectGetHeight(rect) - kNewTabButtonMarginFromEdges -
                     kNewTabButtonDiameter;
   CGFloat leading = CGRectGetWidth(rect) - kNewTabButtonMarginFromEdges -
                     kNewTabButtonDiameter;
   LayoutRect buttonLayout =
       LayoutRectMake(leading, CGRectGetWidth(rect), yOrigin,
                      kNewTabButtonDiameter, kNewTabButtonDiameter);
   return LayoutRectGetRect(buttonLayout);
 }
 
 @end