dartc doesn't parse labels on separate, adjacent case statements

[DartBot]

This issue was originally filed by zundel@google.com

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fails on co19 test: Language/11_Statements/11_Labels_A01_t01.dart

 switch(1) {
    K:
    case 2:
    L:
    case 1:
      break;
    case 0:
    M:
    default:
      N: var x = 0;
  }

file:/home/zundel/dart/tests/co19/src/Language/11_Statements/11_Labels_A01_t01.dart:47: Unexpected token 'case'
    46: L:
    47: case 1:
file:/home/zundel/dart/tests/co19/src/Language/11_Statements/11_Labels_A01_t01.dart:47: Unexpected token 'INTEGER_LITERAL' (expected ';')
    46: L:
    47: case 1:
file:/home/zundel/dart/tests/co19/src/Language/11_Statements/11_Labels_A01_t01.dart:51: Unexpected token 'default'
    50: M:
    51: default:
file:/home/zundel/dart/tests/co19/src/Language/11_Statements/11_Labels_A01_t01.dart:51: Unexpected token ':' (expected ';')
    50: M:
    51: default:
Compilation failed with 4 problems.

[kasperl]

Removed Area-Compiler label.
Added Area-Analyzer label.

[danrubel]

Added this to the M1 milestone.

[DartBot]

This comment was originally written by zundel@google.com

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Added Duplicate label.
Marked as being merged into #2149.