Changed toolchain minor branch to use gcc-4_7-mobile.
Changed toolchain minor branch to use gcc-4_7-mobile.

BUG=none
TEST=remote trybots.

Change-Id: I99065217ecc552236bbfc4c44efb80823da5be40
Reviewed-on: https://gerrit.chromium.org/gerrit/31124
Reviewed-by: Bhaskar Janakiraman <736be64fe54ba1d3a1a479a9970a5fdbcb8cd1a4@chromium.org>
Commit-Ready: asharif <0bffdc695497b480334d6a40467f7e340b20eba1@chromium.org>
Tested-by: asharif <0bffdc695497b480334d6a40467f7e340b20eba1@chromium.org>

zhang0137/chromite,bpsinc-native/src_third_party_chromite,coreos/chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,coreos/chromite,chadversary/chromiumos.chromite,coreos/chromite,bpsinc-native/src_third_party_chromite,zhang0137/chromite,zhang0137/chromite