PPC aftermath: Fix regress-crbug-178790.

The test fails on XP only, so let's tentatively raise the stack limit more. We probably need to investigate what a tighter limit might be and (more importantly) what the underlying reason for the failure is.

Hopefully 1800kB is enough, we can't test this via try jobs, because we don't have XP try bots. :-/

R=machenbach@chromium.org

Review URL: https://codereview.chromium.org/791693005

Cr-Commit-Position: refs/heads/master@{#26092}

test/mjsunit/regress/regress-crbug-178790.js

@@ -25,7 +25,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Flags: --stack-size=1300
+// Flags: --stack-size=1800
 
 // Create a regexp in the form of a?a?...a? so that fully
 // traversing the entire graph would be prohibitively expensive.