This is an work-in-progress CL to prototype using ComPtr.

It also has a new design for internal errors that doesn't use
FormatString, preferring a stream-based approach.

One thing to be aware of is that the address operator does not
behave as expected with ComPtr - we should use ::AddressOf.

BUG=angleproject:530
BUG=angleproject:1644

Change-Id: If5643e9e5726fd9aa5cbd422fca12ae169eb5b1f
Reviewed-on: https://chromium-review.googlesource.com/415027
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>