Temporarily disable calls to OS::TotalPhysicalMemory to avoid ASSERT when running under the Chrome Sandbox.

This CL reverts the behaviour added in r16983 to avoid calling OS::TotalPhysicalMemory
which fails an assert in the Chrome Sandbox.  It reverts the default
ResourceConstraints behaviour to that of V8 before r16983 (i.e., baseing these
values purely on hard-coded checks against 64bit/32bit and Android/non-Android.
This will be reverted once http://crbug.com/312241 has been resolved.

BUG=312241
R=titzer@chromium.org

Review URL: https://codereview.chromium.org/48463002

Patch from Ross McIlroy <rmcilroy@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17415 ce2b1a6d-e550-0410-aec6-3dcde31c8c00