GitLab

This is a reland of 8f219b08 and
9de3faa3 merged into a single change,
with test fixes.

* Changes ModuleCache::Module from a value type to a reference type,
  with ModuleCache maintaining ownership of the Module. ModuleCache
  needs to own its Modules to properly support Windows, which reference
  counts its modules. ModuleCache is retained as a struct to minimize
  the size of this change, but will be changed to a class in a later CL.

* Moves the parallel module caching implementation for Windows into
  ModuleCache. This is required to ensure the referenced modules outlive
  the references to them.  The parallel implementation will be merged
  with the existing module caching implementation over the course of
  later refactoring CLs.

Bug: 931418
Change-Id: Ic58afbf4f7bd48a91d0191a37b623b63501c8fa7
Reviewed-on: https://chromium-review.googlesource.com/c/1483393Reviewed-by: oysteine <oysteine@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Auto-Submit: Mike Wittman <wittman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634872}