[dart2js] Fix ssa tracer

Sometimes the instruction contains newlines (from constant values or
abstract values) which leads to malformed .cfg files.

Change-Id: I2d8a05c97065fae19c42fd914817ff2b75bc7bf3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/446360
Commit-Queue: Nate Biggs <[email protected]>
Reviewed-by: Nate Biggs <[email protected]>
Auto-Submit: Stephen Adams <[email protected]>

Author: rakudrama

pkg/compiler/lib/src/ssa/tracer.dart

@@ -101,6 +101,7 @@ class HTracer extends HGraphVisitor with TracerUtil {
       addIndent();
       String temporaryId = stringifier.temporaryId(instruction);
       String instructionString = stringifier.visit(instruction);
+      instructionString = instructionString.replaceAll('\n', r'\n');
       add("$bci $uses $temporaryId $instructionString $changes $depends <|@\n");
     }
   }