Support jumbo compilation for content/shell (-11 CPU minutes)

Compiling content/shell does in tests consume 13.5 CPU minutes which
is brought down to 2 CPU minutes with jumbo compilation. Jumbo
compilation works by combining many cc files in a single translation
unit, thereby avoiding recompilations of headers and re-instantiation
of templates, as well as by reducing the amount of work needed by the
linker.

Unfortunately IPC message generators can not be combined with other
code since they use some headers under very special circumstances.

Bug: 886902
Change-Id: I4ceee107ea64b774c9f540047182dbcfcf3c487f
Reviewed-on: https://chromium-review.googlesource.com/1238413
Reviewed-by: Peter Beverloo <peter@chromium.org>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#593905}
2 files changed