Change IME hot-key.
Change IME hot-key.

Removed Control+space since it's just for testing. Added Alt+~ which is popular for Japanese IME users on Windows.

We will add more hot-keys like 'Right-Alt+Right-Shift' and 'Zenkaku_Hankaku' later (in a separate CL).

BUG=crosbug/492
TEST=manual

Review URL: http://codereview.chromium.org/1593026

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@44454 0039d316-1c4b-4281-b951-d872f2087c98

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