DevTools: Make Network Conditions Accessible
DevTools: Make Network Conditions Accessible

Network Conditions drawer had following issues:
- Form controls like Network Throttling, User Agent combox box and input box was missing labels for screen reader users.
  This change addresses that issue by adding aria-label to them.
  Additionally, axe test is added for Network Conditions.

Tested keyboard navigation
- navigate up/down drop-down items using arrow keys
- Checkbox is checked/unchecked using space bar
- Tab into/out (no tab traps)

Tested screen reader
- reads checkbox label
- reads items selected from the drop down list

Bug: 963183

Change-Id: I7dec31f1c476f7c63ce4fff9a3b73c1b5377bfc4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1614138
Reviewed-by: Joel Einbinder <bab755abe9fee48fe544272e55f73517d4e4a725@chromium.org>
Commit-Queue: Chandani Shrestha <52538cdd559ab5325fe6b80437501fc583a9e806@microsoft.com>
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#666479}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 8b1245ec9fbba1922502c22e50eb70648a8b33b6

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