Linux: about:memory

(based on http://code.google.com/p/chromium/issues/detail?id=16251)

Add about:memory support to Linux. Rather than try and copy the
Windows output, we use a couple of metrics which make more sense on
Linux: USS and PSS.

http://codereview.chromium.org/177024


git-svn-id: svn://svn.chromium.org/chrome/trunk/src@24979 0039d316-1c4b-4281-b951-d872f2087c98

• base/process_util.h[diff]
• base/process_util_linux.cc[diff]
• chrome/browser/browser_about_handler.cc[diff]
• chrome/browser/browser_resources.grd[diff]
• chrome/browser/memory_details.cc[diff]
• chrome/browser/memory_details.h[diff]
• chrome/browser/memory_details_linux.cc[Added - diff]
• chrome/browser/memory_details_win.cc[Added - diff]
• chrome/browser/renderer_host/render_sandbox_host_linux.cc[diff]
• chrome/browser/renderer_host/render_sandbox_host_linux.h[diff]
• chrome/browser/resources/about_memory_linux.html[diff]
• chrome/browser/zygote_host_linux.cc[diff]
• chrome/browser/zygote_host_linux.h[diff]
• chrome/chrome.gyp[diff]
• chrome/common/child_process_info.cc[diff]
• chrome/common/child_process_info.h[diff]
• chrome/common/temp_scaffolding_stubs.cc[diff]