Merging r155823:

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r155823 | dgregor | 2012-04-30 09:20:27 -0700 (Mon, 30 Apr 2012) | 4 lines

Restore paren, bracket and brace counts in parser when
TentativeParsingAction is reverted, from Pasi Parviainen! Fixes
PR12480 / <rdar://problem/11341251>.

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llvm-svn: 156675