[ios] Improve toolbar in tab_grid

ios/clean/chrome/browser/ui/tab_grid/tab_grid_toolbar.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/tab_grid_toolbar.h"
+
+#import "ios/clean/chrome/browser/ui/tab_grid/ui_stack_view+cr_tab_grid.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+namespace {
+const CGFloat kToolbarHeight = 44.0f;
+}
+
+@implementation TabGridToolbar
+
+- (instancetype)init {
+  if (self = [super init]) {
+    UIVisualEffect* blurEffect =
+        [UIBlurEffect effectWithStyle:UIBlurEffectStyleDark];
+    UIVisualEffectView* toolbarView =
+        [[UIVisualEffectView alloc] initWithEffect:blurEffect];
+    toolbarView.autoresizingMask =
+        UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
+    [self addSubview:toolbarView];
+
+    UIStackView* toolbarContent = [UIStackView cr_tabGridToolbarStackView];
+    [toolbarView.contentView addSubview:toolbarContent];
+
+    // Sets the stackview to a fixed height, anchored to the bottom of the
+    // blur view.
+    toolbarContent.translatesAutoresizingMaskIntoConstraints = NO;
+    [NSLayoutConstraint activateConstraints:@[
+      [toolbarContent.heightAnchor constraintEqualToConstant:kToolbarHeight],
+      [toolbarContent.leadingAnchor
+          constraintEqualToAnchor:toolbarView.contentView.leadingAnchor],
+      [toolbarContent.trailingAnchor
+          constraintEqualToAnchor:toolbarView.contentView.trailingAnchor],
+      [toolbarContent.bottomAnchor
+          constraintEqualToAnchor:toolbarView.contentView.bottomAnchor]
+    ]];
+  }
+  return self;
+}
+
+#pragma mark - UIView
+
+// Returns an intrinsic height so that explicit height constraints are
+// not necessary. Status bar conditional logic can be set using this
+// intrinsic size.
+- (CGSize)intrinsicContentSize {
+  return CGSizeMake(UIViewNoIntrinsicMetric, kToolbarHeight);
+}
+
+@end