Force GC before executing unbox double arrays test to avoid timeouts.

BUG=

Review URL: https://codereview.chromium.org/15292002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14743 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

test/mjsunit/unbox-double-arrays.js

@@ -352,6 +352,9 @@ function testOneArrayType(allocator) {
   assertTrue(%HasFastDoubleElements(large_array));
 }
 
+// Force gc here to start with a clean heap if we repeat this test multiple
+// times.
+gc();
 testOneArrayType(make_object_like_array);
 testOneArrayType(Array);