[iOS][TabStrip] Use data source to identify selected cell in layout

This CL adds a `selectedItem: TabSwitcherItem?` field to TabStripLayout,
which can be used to identify the selected item in the data source when
trying to determine the selected IndexPath of the collection view. This
method yields better results i.e. avoids unnecessary/glitchy looking
layout invalidations when the number of cells changes in the collection
view e.g. while collapsing/expanding groups or closing tabs.

Demo:
https://drive.google.com/file/d/10ep_DsrVheLBkxqWIvQw5mrvPupd0p9c/view

(cherry picked from commit 329d25bbf9e3b846fb498be8572005f3997ec18c)

Change-Id: I51add7d945b055afa2c555a35f500fc529af37d7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5458561
Reviewed-by: Ewann Pellé <ewannpv@chromium.org>
Commit-Queue: Quentin Pubert <qpubert@google.com>
Cr-Original-Commit-Position: refs/heads/main@{#1290793}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5513739
Reviewed-by: Ameur Hosni <ameurhosni@google.com>
Commit-Queue: Ewann Pellé <ewannpv@chromium.org>
Cr-Commit-Position: refs/branch-heads/6422@{#705}
Cr-Branched-From: 9012208d0ce02e0cf0adb9b62558627c356f3278-refs/heads/main@{#1287751}
2 files changed
tree: e03683bf267edc49b35869524c0b879d1a8726c8
  1. android_webview/
  2. apps/
  3. ash/
  4. base/
  5. build/
  6. build_overrides/
  7. buildtools/
  8. cc/
  9. chrome/
  10. chromecast/
  11. chromeos/
  12. codelabs/
  13. components/
  14. content/
  15. courgette/
  16. crypto/
  17. dbus/
  18. device/
  19. docs/
  20. extensions/
  21. fuchsia_web/
  22. gin/
  23. google_apis/
  24. google_update/
  25. gpu/
  26. headless/
  27. infra/
  28. ios/
  29. ipc/
  30. media/
  31. mojo/
  32. native_client_sdk/
  33. net/
  34. pdf/
  35. ppapi/
  36. printing/
  37. remoting/
  38. rlz/
  39. sandbox/
  40. services/
  41. skia/
  42. sql/
  43. storage/
  44. styleguide/
  45. testing/
  46. third_party/
  47. tools/
  48. ui/
  49. url/
  50. webkit/
  51. .clang-format
  52. .clang-tidy
  53. .clangd
  54. .eslintrc.js
  55. .git-blame-ignore-revs
  56. .gitallowed
  57. .gitattributes
  58. .gitignore
  59. .gitmodules
  60. .gn
  61. .mailmap
  62. .rustfmt.toml
  63. .vpython3
  64. .yapfignore
  65. ATL_OWNERS
  66. AUTHORS
  67. BUILD.gn
  68. CODE_OF_CONDUCT.md
  69. codereview.settings
  70. CPPLINT.cfg
  71. DEPS
  72. DIR_METADATA
  73. LICENSE
  74. LICENSE.chromium_os
  75. OWNERS
  76. PRESUBMIT.py
  77. PRESUBMIT_test.py
  78. PRESUBMIT_test_mocks.py
  79. README.md
  80. WATCHLISTS
README.md

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