Enable precision qualifiers.
Enable precision qualifiers.

This enables precision qualifiers to be included in the translated GLSL
and the generated SPIR-V.
We do not enable precision qualifiers on Pixel 2 with Android Q due to
bugs in the Vulkan driver. Issues appear to be fixed with later Android
releases and later devices.

Bug: angleproject:3078
Change-Id: Ia5f40befc7ec80fbb63fb6bbe88600301967f9c9
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2350583
Commit-Queue: Courtney Goeltzenleuchter <aa371ec5c940a0ded89f7ed95bce84faebcf51df@google.com>
Reviewed-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>

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