Begin migrating the vm service from a rest-style interface to a json-rpc style interface.

runtime/vm/coverage.cc

Index: runtime/vm/coverage.cc
diff --git a/runtime/vm/coverage.cc b/runtime/vm/coverage.cc
index 73447618cdb27bc0dea45df47354d8a4ff8c0928..69eadcaeca176ff4952992316d577a84b486c0a3 100644
--- a/runtime/vm/coverage.cc
+++ b/runtime/vm/coverage.cc
@@ -271,7 +271,6 @@ void CodeCoverage::PrintJSON(Isolate* isolate,
   Class& cls = Class::Handle();
   JSONObject coverage(stream);
   coverage.AddProperty("type", "CodeCoverage");
-  coverage.AddProperty("id", "coverage");
   {
     JSONArray jsarr(&coverage, "coverage");
     for (int i = 0; i < libs.Length(); i++) {