Expose thumbnails of pages to iOS share extensions.

ios/chrome/browser/ui/activity_services/share_to_data_builder.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.
+
+#include "ios/chrome/browser/ui/activity_services/share_to_data_builder.h"
+
+#include "base/logging.h"
+#include "ios/chrome/browser/tabs/tab.h"
+#include "ios/chrome/browser/ui/activity_services/chrome_activity_item_thumbnail_generator.h"
+#include "ios/chrome/browser/ui/activity_services/share_to_data.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+namespace activity_services {
+
+ShareToData* ShareToDataFromTab(Tab* tab) {
+  // For crash documented in crbug.com/503955, tab.url which is being passed
+  // as a reference parameter caused a crash due to invalid address which
+  // which suggests that |tab| may be deallocated along the way. Check that
+  // tab is still valid by checking webState which would be deallocated if
+  // tab is being closed.
+  if (!tab.webState)
+    return nil;
+  DCHECK(tab);
+  // If the original page title exists, it is expected to match the tab title.
+  // If this ever changes, then a decision has to be made on which one should
+  // be used for sharing.
+  DCHECK(!tab.originalTitle || [tab.originalTitle isEqualToString:tab.title]);
+  BOOL isPagePrintable = [tab viewForPrinting] != nil;

[Olivier, 2017/01/20 10:14:00]

C++ case

[jif, 2017/01/24 10:29:50]

It's an obj-c++ function with no c++ functionality used (except the namespace
outside).

+  ThumbnailGenerator thumbnailGenerator =
+      activity_services::thumbNailGeneratorForTab(tab);
+  return [[ShareToData alloc] initWithURL:tab.url
+                                    title:tab.title
+                          isOriginalTitle:(tab.originalTitle != nil)
+                          isPagePrintable:isPagePrintable
+                       thumbnailGenerator:thumbnailGenerator];
+}
+
+}  // namespace activity_services