Memory profile tables should scroll together

[elliette]

When a developer enables "Advanced developer settings" from the general DevTools setting dialog, the Memory panel includes a table that shows GC statistics.

This table is above the memory profile table, and looks like it is part of the memory profile table. However, the two tables are separate, and scroll separately.

We should figure out a way to get them to scroll horizontally together, possibly by adding a MultiTable widget that supports multiple tables.

[SanskaarUndale21]

@elliette
i have mentioned approch i used and some details dont mind the commits i still have to work on them but overall my approch is that

Fix: GC Stats and Allocation Profile tables now scroll horizontally in sync

Root cause

Each FlatTable widget creates its own internal ScrollController for horizontal scrolling using
TableControllerBase.initScrollController().

The GC Statistics table and the Allocation Profile table were completely independent.
Dragging one scrollbar had no effect on the other, even though both tables have identical column structures
in advanced developer mode:

• Total, New Space, Old Space
• 4 columns each
• Total width: 1160 px

Approach

Instead of introducing a MultiTable wrapper, an optional horizontalScrollController parameter was added to FlatTable.

When this parameter is provided:

• FlatTableController sets the inherited horizontalScrollController before initScrollController() runs
• initScrollController() checks if a controller already exists and only creates one if it is null

Controller ownership is tracked:

• TableControllerBase.dispose() only disposes the controller if it created it
• If a shared controller is injected, the caller manages its lifecycle

AllocationProfileTableViewState now:

• Creates a single shared ScrollController
• Passes it to both _GCStatsTable and _AllocationProfileTable
• Disposes it in its own dispose()

Files changes

lib/src/shared/table/table_controller.dart

• FlatTableController constructor now accepts optional ScrollController? horizontalScrollController
• Sets this.horizontalScrollController before initialization
• initScrollController() only creates a controller if none exists
• _ownsHorizontalScrollController is set only when internally created
• dispose() only disposes when owned

lib/src/shared/table/_flat_table.dart

• FlatTable now has optional horizontalScrollController
• Passed to FlatTableController inside _setUpTableController()

lib/src/screens/memory/panes/profile/profile_view.dart

• AllocationProfileTableViewState creates a shared ScrollController
• Disposes it properly
• Passes it to both tables
• _GCStatsTable and _AllocationProfileTable accept and forward the controller

Behaviour

• With advanced developer settings off
  Only the Allocation Profile table is shown
  No change in behavior

• With advanced developer settings on
  Both tables share the same ScrollController
  Scrolling either table moves both in sync

• Column alignment remains exact
  200 px class column + 12 columns of 80 px = 1160 px
  Both tables stay perfectly aligned at all scroll positions

• All other FlatTable usages remain unchanged

Backward compatibility

The horizontalScrollController parameter is optional and defaults to null.

All existing FlatTable usages continue to work without modification.

Ownership tracking in TableControllerBase prevents double disposal in all scenarios.