GitLab

Adds tests for the Hunspell fallback logic (Windows hybrid spell checking)
submitted here:
https://chromium-review.googlesource.com/c/chromium/src/+/1918277

- Adds browser tests for SpellCheckHostChromeImpl
- Adds component tests for the new SpellcheckHostMetrics
- Adds component test coverage for the new SpellcheckPlatform methods in the
  Windows platform test
    - Created a bug to track splitting the single test into multiple ones
- Adds component tests for SpellcheckProvider
    - Creates a new FakeSpellCheck class to fake the count of enabled spell
      check locales, which is needed to control when to call into the
      browser spell checker

Bug: 463364, 1035450
Change-Id: Ie3e692c0d5d5970ed2ab7612018198bf42049139
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1972573
Auto-Submit: Guillaume Jenkins <gujen@google.com>
Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Commit-Queue: Rouslan Solomakhin <rouslan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726150}