Address Nested ConstraintLayouts in search & tabs tray experiences

[mcomella]

Blocked by #15280 & #15644. They are addressed.

20ms tabs tray improvement.

Please remove the nested ConstraintLayouts in the search screen and tabs tray. From a correctness and performance perspective, ConstraintLayouts are designed to minimize nesting which improves perf and reduces battery use. Ideally, ConstraintLayout is the root element and contains only leaf nodes.

We added a custom lint rule #15280 to check for nested ConstraintLayouts. In order to work on this bug:

• Delete the app/lint-baseline.xml file (it only contains these violations)
• Run ./gradlew lintDebug and check the violation output
• Fix the associated errors; be careful about how accessibility may change
• (when completed) Create a new baseline file with any remaining violations

WARNING: replacing a ConstraintLayout with several nested ViewGroups is unlikely to improve performance. Remember, a goal is to reduce nesting. If you're unable to remove the extra ConstraintLayout(s) without doing this, it's probably better to suppress this violation.

Please ask the performance team if you have questions!

┆Issue is synchronized with this Jira Task

[liuche]

Two screens involved. Can also run some performance tests (ask the perf team) afterwards.

[mcarare]

For QA: There is no specific testing needed, just check that the layout changes did not introduce any regressions in behavior. Thank you!

[sflorean]

Tested on latest Nightly 11/19 and we didn't encounter any new issue. Devices:

• Pixel 3 (Android 11)
• LG G7 (Android 8.0).