Add CrashReportMimeWriter to MIME encode crashpad minidumps

CrashReportMimeWriter provides a method to call into native code to
rewrite the minidumps as MIME messages. This CL also links that native
code into webview and clank, but makes no functional changes.

Bug: crashpad:30
Change-Id: Ief41d366614a833db3b643f46a0297c52fea495f
Reviewed-on: https://chromium-review.googlesource.com/1115702
Commit-Queue: Joshua Peraza <jperaza@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Peter Wen <wnwen@chromium.org>
Reviewed-by: agrieve <agrieve@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581918}
9 files changed