Telemetry / Android: do not crash on GetCpuStats() if the process is gone.

Some bots are failing with:
...[0].split()
IndexError: list index out of range
This can specially happen on page cyclers,
since multiple renders can be started and killed by the
framework.

BUG=

Review URL: https://codereview.chromium.org/25002005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226642 0039d316-1c4b-4281-b951-d872f2087c98
[Android WebView] OnMemoryPressure to drop tile memory

In OnMemoryPressure, drop tiles on invisible browser views.

Not reusing base::MemoryPressureListener because Android
WebView requires onTrimMemory to be called synchronously.

BUG=
NOTRY=true

Review URL: https://codereview.chromium.org/25082006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226643 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226642
SVN changes up to revision 226643