Fix a pair of bugs in the translation of 'if' nodes.
Fix a pair of bugs in the translation of 'if' nodes.

The condition graph fragment was appended twice, and the join did not
properly handle the case of nonlocal exits from the arms of the 'if'.

R=srdjan@google.com
BUG=
TEST=all tests pass in x64 release mode with --use_new_compiler

Review URL: https://chromiumcodereview.appspot.com//9456009

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@4545 260f80e4-7a28-3924-810f-c04153c831b5

dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk