Add base::get to support rvalue-reference tuple

std::get in libstdc++4.6 doesn't have a overload for rvalue-reference
tuple. That implies std::get<0>(std::make_tuple(1)) is `const int&`,
instead of `int&&`.
This CL add base::get with correct type.

Review-Url: https://codereview.chromium.org/2047013002
Cr-Commit-Position: refs/heads/master@{#401758}


CrOS-Libchrome-Original-Commit: ec749b1eeaa49a45973e651e870ed16531c8b0d9
2 files changed
tree: 820882cd473849501469eefecd6e5f1623bde8b7
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/