Fixes bug in about:memory that resulted in showing null for browser if you had a crashed tab or phantom tab.
Fixes bug in about:memory that resulted in showing null for browser if
you had a crashed tab or phantom tab.

BUG=none
TEST=create two tabs, pin one, close it (so that it goes phantom),
  navigate to about:memory and make sure you don't see an entry for
  the
  phantom tab.

Review URL: http://codereview.chromium.org/646035

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@39399 0039d316-1c4b-4281-b951-d872f2087c98

gavinp/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,ropik/chromium,adobe/chromium,adobe/chromium,ropik/chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,gavinp/chromium,adobe/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,gavinp/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,adobe/chromium,yitian134/chromium,ropik/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,ropik/chromium,yitian134/chromium,ropik/chromium,gavinp/chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,ropik/chromium,adobe/chromium,ropik/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,gavinp/chromium