Encapsulate the split view in a new class

[sangwoo108]

Previously,

• BrowserView was responsible for managing the split view.
• ContentsContainer has two web view, and two dev tools, which would weird view hierarchy.

This PR introduces SplitView class and it encapsulate operations related to split view. And split view contains two ContentsContainer, so that we don't reuse upstream's contents container as is.

Also this change doesn't intend to change the behavior. The existing test like SplitViewBrowserTest and SplitViewLayoutManagerTest would check the regression.

Resolves brave/brave-browser#39542

Submitter Checklist:

• I confirm that no security/privacy review is needed and no other type of reviews are needed, or that I have requested them
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally:
  • npm run test -- brave_browser_tests, npm run test -- brave_unit_tests wiki
  • npm run presubmit wiki, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

No behavior changes.

[simonhong]

Regressions from this PR.

• Window resizing is too slow fixed
• Flashing whenever change active tab in split view fixed

Whenever active tab changes in a same tile, we set different styled borfer to active/inactive tabs.
As each border's thickness are different, it causes re-layout in each tab container.
and this causes flashing whenever active tab changes.
When same thickness is used, not flickered. => Fixed by using same thickness.

[fallaciousreasoning]

lgtm @simonhong

[github-actions]

[puLL-Merge] - brave/brave-core@24478

Description

This PR significantly refactors the split view functionality in the Brave browser. It introduces a new SplitView class and reorganizes related code, improving the structure and maintainability of the split view feature.

Changes

Changes

1. browser/ui/views/split_view/split_view.cc and split_view.h:

   • New SplitView class introduced, encapsulating split view functionality
   • Handles layout, visibility, and management of secondary web views and devtools

2. browser/ui/views/split_view/split_view_layout_manager.cc and split_view_layout_manager.h:

   • New SplitViewLayoutManager class for managing the layout of split view components

3. browser/ui/views/frame/brave_browser_view.cc and brave_browser_view.h:

   • Removed direct management of split view components
   • Now uses SplitView class for split view functionality

4. browser/ui/BUILD.gn:

   • Updated build configuration to include new split view files
   • Removed references to deleted files

5. Various test files:

   • Updated to work with the new SplitView structure
   • Some tests moved to new locations

6. Removed files:

   • brave_contents_layout_manager.cc and brave_contents_layout_manager.h
   • split_view_location_bar.cc and split_view_location_bar.h (moved to new location)

sequenceDiagram
    participant BraveBrowserView
    participant SplitView
    participant SplitViewLayoutManager
    participant ContentsWebView
    participant SecondaryContentsWebView

    BraveBrowserView->>SplitView: Create
    SplitView->>SplitViewLayoutManager: Create
    SplitView->>ContentsWebView: Manage
    SplitView->>SecondaryContentsWebView: Manage
    BraveBrowserView->>SplitView: WillChangeActiveWebContents
    SplitView->>SplitViewLayoutManager: UpdateLayout
    BraveBrowserView->>SplitView: DidChangeActiveWebContents
    SplitView->>ContentsWebView: UpdateVisibility
    SplitView->>SecondaryContentsWebView: UpdateVisibility

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Possible Issues

• The refactoring may introduce temporary instability or bugs in the split view functionality.
• Some existing tests may need further adjustment to work with the new structure.

Security Hotspots

No significant security hotspots identified in this refactoring.

[simonhong]

@bridiver PTAL when you're available.

[simonhong]

@bridiver Kindly ping.