Manual revert of r159605 due to severe performance regressions.

"Free an empty partitionAlloc partition page even if it is the last page."
Seems like this was a bad idea.

That CL did include some useful new ASSERTs and a failure to initialize a
variable to zero, so I left them in during the manual revert (code had changed
too much for an automatic revert).

BUG=307846,307849
TBR=tsepez@chromium.org

Review URL: https://codereview.chromium.org/31883002

git-svn-id: svn://svn.chromium.org/blink/trunk@160073 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Layout toplevel timeline panel elements using flex.

R=pfeldman@chromium.org, caseq, pfeldman

Review URL: https://codereview.chromium.org/26205005

git-svn-id: svn://svn.chromium.org/blink/trunk@160074 bbb929c8-8fbe-4397-9dbb-9b2b20218538