Switch to using TCMALLOC in browser process to fix WinHeap hanging IO thread for 15 secs.
Switch to using TCMALLOC in browser process to fix WinHeap hanging IO thread for 15 secs.

Note that the renderer process is still using TCMALLOC, and this only changes the default in the browser process.

BUG=83285
TEST=memory unit tests
R=jar
Review URL: http://codereview.chromium.org/7047018

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@85998 0039d316-1c4b-4281-b951-d872f2087c98

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