Make CompilerTask independent of compiler.

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

Index: pkg/compiler/lib/src/ssa/builder.dart
diff --git a/pkg/compiler/lib/src/ssa/builder.dart b/pkg/compiler/lib/src/ssa/builder.dart
index 5b13bbcf88af235da6e93c2f06a294180080f115..76070774a5bff3f0d5b9cf3d2f4196cee0c3ff2f 100644
--- a/pkg/compiler/lib/src/ssa/builder.dart
+++ b/pkg/compiler/lib/src/ssa/builder.dart
@@ -91,13 +91,15 @@ class SsaBuilderTask extends CompilerTask {
   final CodeEmitterTask emitter;
   final JavaScriptBackend backend;
   final SourceInformationStrategy sourceInformationFactory;
+  final Compiler compiler;
 
   String get name => 'SSA builder';
 
   SsaBuilderTask(JavaScriptBackend backend, this.sourceInformationFactory)
       : emitter = backend.emitter,
         backend = backend,
-        super(backend.compiler);
+        compiler = backend.compiler,
+        super(backend.compiler.measurer);
 
   DiagnosticReporter get reporter => compiler.reporter;