Add mmap and native heap classifiers to memory_inspector.
    
This introduces the final piece to the classifier which are
able to do basic parsing for mmap and native heap traces.
    
BUG=340294
NOTRY=true

Review URL: https://codereview.chromium.org/184043006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255933 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255933