When converting to mojo FramePolicy I faced 2 bitfields (http://crrev/c/784372):

- WebInsecureRequestPolicy [1] - A plain uint8_t bitfield, serialized as uint8 on Mojo interface [2].
- WebSandboxFlags [3] - An enum class bitfield with some constexpr for overloading some operators. In Mojo represented as a duplicated [[Extensible]] enum [4].


This bug is to track possibility to improve Mojo support for this sort of types because the typemap felt as unnecessary work and duplicated some definitions.

A simplistic assessment brings the number of potential candidates to ~150 types; enum/enum class with bit shifts (likely to be bitfield):
$ git ls-files | grep -E '*\.(cc|cpp|h)$' | xargs egrep  -A 7  "^\s*enum (class .* : .*int.*)?" | egrep "k.* = 1 << 1"   |wc -l  
152      


[1] - https://cs.chromium.org/chromium/src/third_party/WebKit/public/platform/WebInsecureRequestPolicy.h
[2] - https://cs.chromium.org/chromium/src/content/common/frame.mojom
[3] - https://cs.chromium.org/chromium/src/third_party/WebKit/common/sandbox_flags.h
[4] - https://cs.chromium.org/chromium/src/third_party/WebKit/common/feature_policy/feature_policy.mojom