When the scrolling position is restored and the URL contains an anchors (i.e. https://example.com/index.html#anchor), there is some indeterminism.
We get different results depending on which function is called first between:
- FrameLoader::ProcessFragment()
- FrameLoader::RestoreScrollPositionViewState().

Currently, a way to chose in test which function will be called first is to increase/decrease the size of the main response.
Example: https://chromium-review.googlesource.com/c/chromium/src/+/962804
______________________________________________________________________________

Description of what happens in the current code:

1) When ProcessFragment() is called first:

  a) ProcessFragment():
  Several scrollable layers are scrolled such that the anchor is
  displayed. It may includes the root one, but also some children.

  b) RestoreScrollPositionAndViewState():
  The root layer is scrolled using what is stored in the HistoryItem. It
  overrides the scroll done in a) for the root layer. Children layers
  are not overridden.

2) When RestoreScrollPositionAndViewState() is called first:

  a) RestoreScrollPositionAndViewState():
  The root layer is scrolled using what is stored in the HistoryItem.
  Children layers are not scrolled.

  b) ProcessFragment():
  Nothing happens because InitialScrollState::did_restore_from_history
  has been set to true in a). The ProcessFragment() will skip the
  fragment scroll.

At the end, the difference is that the children layers are scrolled in
1), but not in 2).
______________________________________________________________________________


 

When the scrolling position is restored and the URL contains an anchors (i.e. https://example.com/index.html#anchor), there is some non-determinism.
We get different results depending on which function is called first between:
- FrameLoader::ProcessFragment()
- FrameLoader::RestoreScrollPositionViewState().

Currently, a way to chose in test which function will be called first is to increase/decrease the size of the main response.
Example: https://chromium-review.googlesource.com/c/chromium/src/+/962804
______________________________________________________________________________

Description of what happens in the current code:

1) When ProcessFragment() is called first:

  a) ProcessFragment():
  Several scrollable layers are scrolled such that the anchor is
  displayed. It may includes the root one, but also some children.

  b) RestoreScrollPositionAndViewState():
  The root layer is scrolled using what is stored in the HistoryItem. It
  overrides the scroll done in a) for the root layer. Children layers
  are not overridden.

2) When RestoreScrollPositionAndViewState() is called first:

  a) RestoreScrollPositionAndViewState():
  The root layer is scrolled using what is stored in the HistoryItem.
  Children layers are not scrolled.

  b) ProcessFragment():
  Nothing happens because InitialScrollState::did_restore_from_history
  has been set to true in a). The ProcessFragment() will skip the
  fragment scroll.

At the end, the difference is that the children layers are scrolled in
1), but not in 2).
______________________________________________________________________________


 

When the scrolling position is restored and the URL contains an anchors (i.e. https://example.com/index.html#anchor), there is some non-determinism.
We get different results depending on which function is called first between:
- FrameLoader::ProcessFragment()
- FrameLoader::RestoreScrollPositionViewState().

Currently, a way to choose in test which function will be called first is to increase/decrease the size of the main response.
Example: https://chromium-review.googlesource.com/c/chromium/src/+/962804
______________________________________________________________________________

Description of what happens in the current code:

1) When ProcessFragment() is called first:

  a) ProcessFragment():
  Several scrollable layers are scrolled such that the anchor is
  displayed. It may includes the root one, but also some children.

  b) RestoreScrollPositionAndViewState():
  The root layer is scrolled using what is stored in the HistoryItem. It
  overrides the scroll done in a) for the root layer. Children layers
  are not overridden.

2) When RestoreScrollPositionAndViewState() is called first:

  a) RestoreScrollPositionAndViewState():
  The root layer is scrolled using what is stored in the HistoryItem.
  Children layers are not scrolled.

  b) ProcessFragment():
  Nothing happens because InitialScrollState::did_restore_from_history
  has been set to true in a). The ProcessFragment() will skip the
  fragment scroll.

At the end, the difference is that the children layers are scrolled in
1), but not in 2).
______________________________________________________________________________