Disable GPU raster for OSX 10.9
Disable GPU raster for OSX 10.9

crbug.com/611310 contains a report of a rendering issue on 10.9. As I
haven't been able to repro locally, I was hoping to get more data on
this issue during beta/canary, but no additional reports have come in.
In order to allow us to launch to stable with lower risk, this CL
disables GPU raster on 10.9, which only accounts for ~7% of mac users.

We may re-enable this for M53 Beta M54 Canary in order to track down the
issue in question, and hopefully launch to 10.9 in M53.

BUG=611310
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2151393002
Cr-Commit-Position: refs/heads/master@{#405902}
(cherry picked from commit 51630e3efbcde407cdc7c4e0f35cba88a2090601)

Review URL: https://codereview.chromium.org/2154343003 .

Cr-Commit-Position: 03d981dee550804c6934fd1a1d9cfa3c172affd3@{#668}
Cr-Branched-From: e9621a186760eb36d74098d9e33e4dd91c427b34@{#394939}

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