ime: Use new style enum for ImeSwitchType.

Use the new style for histogram enums [1]

[1] https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histograms/README.md#enum-histograms

TBR=sky@chromium.org

Bug: 953901
Change-Id: Icc8311ebfc17eac7a47113a0eb38259231ca1a95
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1621412
Reviewed-by: Darren Shen <shend@chromium.org>
Commit-Queue: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661589}
4 files changed