Oilpan: Convert a raw pointer in ChromePluginPrintContext to a Member.
Oilpan: Convert a raw pointer in ChromePluginPrintContext to a Member.

The containing class, ChromePluginPrintContext, is already Oilpan-managed.

BUG=509911
R=haraken@chromium.org, keishi@chromium.org, oilpan-reviews@chromium.org

Review URL: https://codereview.chromium.org/1257303002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@199632 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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