Condense multiple occlusion change notifications into 1 re-mirror.

This fix is actually not strictly necessary after
https://crrev.com/c/5659468, but it's a good thing to do to
fortify the code if there's another hidden case like this.

If the WindowOcclusionTracker should detect lots of occlusion
changes in one pass, it sends a bunch of observer notifications
in one loop on the main thread:
https://screenshot.googleplex.com/8sfxQqgmNQxskJQ.png

The current code leads to a bunch of
RecreateDeskContentsMirrorLayers() calls:
https://screenshot.googleplex.com/4TXZ9LDSK2Ytsoi.png

This is unnecessary and very expensive. All that's needed is one
RecreateDeskContentsMirrorLayers() that will capture all of the
occlusion changes in one mirroring tree re-build.

As stated above, it should be very unusual to see so many
occlusion changes in a desk while the desk bar is active, but
this weakness is being addressed if there's a case we're not
thinking of.

Bug: b:294094124
Change-Id: Ia91cb1122774464af381811766c2b43caee2d4b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5660285
Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Eric Sum <esum@google.com>
Cr-Commit-Position: refs/heads/main@{#1320587}
2 files changed
tree: 961044dab12f684a55f02e802f6a72d783d8b976
  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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