Better tracking of provided types at call sites

lib/compiler/implementation/ssa/builder.dart

Index: lib/compiler/implementation/ssa/builder.dart
diff --git a/lib/compiler/implementation/ssa/builder.dart b/lib/compiler/implementation/ssa/builder.dart
index 8a2d33a4108cb9ced2661e73ee6a18dee2b61b65..c923ce3d8d121ac8e7448c076fc6f941bf3d777d 100644
--- a/lib/compiler/implementation/ssa/builder.dart
+++ b/lib/compiler/implementation/ssa/builder.dart
@@ -178,17 +178,29 @@ class SsaBuilderTask extends CompilerTask {
 
       // If there is an estimate of the parameter types assume these types when
       // compiling.
+      OptionalParameterTypes defaultValueTypes = null;
+      FunctionSignature signature = element.computeSignature(compiler);
+      if (signature.optionalParameterCount > 0) {
+        defaultValueTypes =
+            new OptionalParameterTypes(signature.optionalParameterCount);
+        int index = 0;
+        signature.forEachOptionalParameter((Element parameter) {
+          Constant defaultValue = compiler.compileVariable(parameter);
+          HType type = HGraph.mapConstantTypeToSsaType(defaultValue);
+          defaultValueTypes.update(index, parameter.name, type);
+          index++;
+        });
+      }
       HTypeList parameterTypes =
-          backend.optimisticParameterTypes(
-              element);
+          backend.optimisticParameterTypes(element, defaultValueTypes);
       if (!parameterTypes.allUnknown) {
-        FunctionSignature signature = element.computeSignature(compiler);
         int i = 0;
         signature.forEachParameter((Element param) {
           builder.parameters[param].guaranteedType = parameterTypes[i++];
         });
       }
-      backend.registerParameterTypesOptimization(element, parameterTypes);
+      backend.registerParameterTypesOptimization(
+          element, parameterTypes, defaultValueTypes);
 
       if (compiler.tracer.enabled) {
         String name;