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"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+@interface SuggestionsCoordinator ()<SuggestionsCommands> {
+  UINavigationController* _navigationController;
+}
+
+@end
+
+@implementation SuggestionsCoordinator
+
+- (void)start {
+  if (_navigationController) {
+    // Prevent this coordinator to be started twice in a row.

[marq (ping after 24h), 2017/01/19 16:32:31]

Ideally this would be the problem of the code that owns the coordinator.

[gambard, 2017/01/19 17:50:12]

I can add a "running" property and check it in the BVC. Is it better?

[lpromero, 2017/01/19 18:49:13]

I think there is a fundamental problem here: the BVC never resets its
coordinator ivar (scoped_nsobject), except when asked to clear all presented UI.
So in the normal case, how do you dismiss the Suggestions UI?

[gambard, 2017/01/20 07:37:43]

In the normal case, the suggestion UI has a "done" button calling stop. See line
39.

[lpromero, 2017/01/20 08:58:02]

Ah missed that one! I think I looked for " stop];" so I didn't see it. Thanks!

[lpromero, 2017/01/20 08:58:02]

At some point in the New Architecture we'll need this coordinator to report to
its parent, which will be the one calling -stop. Is it worth doing now, instead
of a workaround?

[gambard, 2017/01/20 12:22:17]

For now the parent is BVC, not sure that adding code to it is a good idea.
I think it is OK for now to keep the guard here.

[marq (ping after 24h), 2017/01/20 12:34:46]

Again, I think the object creating the coordinator should be able to keep track
of whether it has created and started one yet or not. I don't like the idea of
-start being a no-op sometimes. 

[gambard, 2017/01/23 09:45:54]

As we discussed it, what solution do you suggest?

+    return;
+  }
+
+  SuggestionsViewController* suggestionsViewController =
+      [[SuggestionsViewController alloc]
+          initWithStyle:CollectionViewControllerStyleDefault];
+
+  suggestionsViewController.suggestionCommandHandler = self;
+  _navigationController = [[UINavigationController alloc]
+      initWithRootViewController:suggestionsViewController];
+
+  suggestionsViewController.navigationItem.leftBarButtonItem =
+      [[UIBarButtonItem alloc]
+          initWithTitle:l10n_util::GetNSString(IDS_IOS_SUGGESTIONS_DONE)
+                  style:UIBarButtonItemStylePlain
+                 target:self
+                 action:@selector(stop)];
+
+  [self.baseViewController presentViewController:_navigationController
+                                        animated:YES

[marq (ping after 24h), 2017/01/19 16:32:32]

self.context.animated? Not sure if that landed yet.

[lpromero, 2017/01/19 17:42:40]

Not yet in ios/chrome. I will make a new pass when I decide to move forward with
it in ios/chrome, so this can stay as is in this CL.

+                                      completion:nil];
+}
+
+- (void)stop {
+  [[_navigationController presentingViewController]
+      dismissViewControllerAnimated:YES
+                         completion:nil];
+  _navigationController = nil;
+}
+
+#pragma mark - SuggestionsCommands
+
+- (void)openReadingList {
+}
+
+- (void)openFirstPageOfReadingList {
+}
+
+- (void)addEmptyItem {
+}
+
+@end