Make the spellcheck-context-menu generation code more robust/future-proof (fil and fil-PH will match each other).  Currently, en-AU, de-CH, fr-CA do not match any spellcheck language. With this change, they will match en-US, de-DE, fr-FR, respectively unless  there's an exact (more specific) match. Matching en-{AU,NZ,ZA} with en-US is not ideal.
Make the spellcheck-context-menu generation code more robust/future-proof (fil and fil-PH will match each other). 
Currently, en-AU, de-CH, fr-CA do not match any spellcheck language. With
this change, they will match en-US, de-DE, fr-FR, respectively unless 
there's an exact (more specific) match. Matching en-{AU,NZ,ZA} with en-US
is not ideal.

BUG=5251
TEST=Add 'fr-CA' (but NOT fr or fr-FR) to the accept-language list and see if 'fr-FR' comes up
in the list of spell-check languages in the context menu of a textarea. Add 'de' (but not de-DE) to a-l list and see if 'de-DE' comes up in the list of spell-check languages in the context menu. 


Review URL: http://codereview.chromium.org/13262

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@6562 0039d316-1c4b-4281-b951-d872f2087c98

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