The 17763 version of d3dcompiler_47.dll contains some new bug fixes and other things that Angle wants. But, it uses the UCRT (universal CRT) which means that by default it does not run on all Windows 7 machines.

This caused some problems when rolling the toolchain (see  crbug.com/919163 ) so eventually a new toolchain/SDK was rolled without upgrading this DLL. There are three possibilities for how to move forwards:

1) Ship the new DLL and let the (unknown but small) number of Windows 7 users who can't load the DLL fall back to SwiftShader. This is simplest but has unclear implications for an unknown number of users.
2) Ship the new DLL and the old one and fall back to the old DLL if the new one fails to load. This is fairly simple but it strands some unknown number of users on the old (buggy) version and it means distributing ~3.6 MB of excess binary data.
3) Ship the new DLL and the UCRT files that it needs. This is the most complex solution (both isolates and the installer must separately have the extra 42 files included) and it will cause some amount of downstream pain (CEF, Opera, and others must also ship these DLLs) and it adds ~2 MB of excess binary data for the UCRT but it is the "correct" fix.

I'm leaning toward #3, despite the disruption.

Thoughts?