[Android WebView] Change tile size to 384

512x512 tiles uses exactly 1MB in memory. However the allocator
on certain devices allocates 1.25MB instead (due to performance
heuristics), so 20% of allocated tile memory is wasted in this
case.

Determined experimentally that 384 tiles do not have any overhead, so
update tile size to 384.

Also reduce the number of resources per webview from 200 to 150 to
overcome potential file handle limit problems, and add a command line
switch to control this value.

Internal bug b/11446261

BUG=
NOTRY=true

Review URL: https://codereview.chromium.org/56083003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232457 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232457
Exclude test that fails only on official builds.

BUG=230471
NOTRY=true

Review URL: https://codereview.chromium.org/56273002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232458 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232458