Add the suggestions UI in chrome

ios/chrome/browser/suggestions/suggestions_coordinator.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/chrome/browser/suggestions/suggestions_coordinator.h"
+
+#include "base/mac/scoped_nsobject.h"
+#import "ios/chrome/browser/ui/suggestions/suggestions_commands.h"
+#import "ios/chrome/browser/ui/suggestions/suggestions_view_controller.h"
+#include "ios/chrome/grit/ios_strings.h"
+#include "ui/base/l10n/l10n_util.h"
+
+@interface SuggestionsCoordinator ()<SuggestionsCommands> {
+  base::scoped_nsobject<UINavigationController> _navigationController;
+}
+
+@end
+
+@implementation SuggestionsCoordinator
+
+- (void)start {
+  if (_navigationController) {
+    // Prevent this coordinator to be started twice in a row.

[lpromero, 2017/01/18 14:37:07]

I am not sure if we want to philosophically do it that way. Because that would
mean doing it in all coordinators, or having two types of coordinators. (That
could be a setting in the context though.)

Mark, do you have feedback on that?

[gambard, 2017/01/18 16:54:04]

I don't know if we want to do it that way but we are already doing it (in
AlertCoordinator for example).

+    return;
+  }
+
+  SuggestionsViewController* suggestionsViewController =
+      [[[SuggestionsViewController alloc]
+          initWithStyle:CollectionViewControllerStyleDefault] autorelease];
+
+  suggestionsViewController.suggestionCommandHandler = self;
+  _navigationController.reset([[UINavigationController alloc]
+      initWithRootViewController:suggestionsViewController]);
+
+  suggestionsViewController.navigationItem.leftBarButtonItem =
+      [[[UIBarButtonItem alloc]
+          initWithTitle:l10n_util::GetNSString(IDS_IOS_SUGGESTIONS_DONE)
+                  style:UIBarButtonItemStylePlain
+                 target:self
+                 action:@selector(stop)] autorelease];
+
+  [self.baseViewController presentViewController:_navigationController
+                                        animated:YES
+                                      completion:nil];
+}
+
+- (void)stop {
+  [[_navigationController presentingViewController]
+      dismissViewControllerAnimated:YES
+                         completion:nil];
+  _navigationController.reset();
+}
+
+#pragma mark - SuggestionsCommands
+
+- (void)openReadingList {
+}
+
+- (void)openFirstPageOfReadingList {
+}
+
+- (void)addEmptyItem {
+}
+
+@end