Make plugin processes (except Gears) run at normal priority.
Make plugin processes (except Gears) run at normal priority.

This fixes a lot of the spurious unresponsive plugin dialogs, and also makes it so that the browser process isn't hung waiting for a low priority plugin process when cpu usage is high.

I was able to simulate this by using 100% cpu in a test program.  Before this change, the dialog always comes up and a flash video never plays.  The browser process is also hung.  With this change the video plays and I can interact with the browser.
Review URL: http://codereview.chromium.org/7129

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@3323 0039d316-1c4b-4281-b951-d872f2087c98

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