Fix tests regress-336820 and regress-678917.

Execution tests regress-336820 and regress-678917 finished with error
messages "allocation failure GC in old space requested" and "fatal
javascript OOM in CALL_AND_RETRY_LAST". For successful execution,
parameter max_old_space_size must be increased and this is done inside
tests.

TEST=mjsunit/regress/regress-336820,
     mjsunit/regress/regress-678917
BUG=

Review-Url: https://codereview.chromium.org/2907363003
Cr-Commit-Position: refs/heads/master@{#45672}

test/mjsunit/regress/regress-336820.js

@@ -25,6 +25,8 @@
 // (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: --max-old-space-size=400
+
 assertThrows((function() {
   s = "Hello World!\n";
   while (true) {

test/mjsunit/regress/regress-678917.js

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --max-old-space-size=270
+
 s1 = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx';
 s1 += s1;
 s1 += s1;