Add more unit tests for JS bindings to Core

mojo/public/bindings/js/test/harness.cc

Index: mojo/public/bindings/js/test/harness.cc
diff --git a/mojo/public/bindings/js/test/harness.cc b/mojo/public/bindings/js/test/harness.cc
index b4b81f472ac1d4a7378412e8d1c3e546d31aa1ac..5b7319d718a08739f18f25316679d86cfc885508 100644
--- a/mojo/public/bindings/js/test/harness.cc
+++ b/mojo/public/bindings/js/test/harness.cc
@@ -32,6 +32,12 @@ class TestRunnerDelegate : public RunnerDelegate {
   }
 };
 
+std::string GetExceptionInfo(const v8::TryCatch& try_catch) {
+  std::string info;
+  gin::ConvertFromV8(try_catch.Message()->Get(), &info);
+  return info;
+}
+
 void RunTestFromFile(const base::FilePath& path) {
   EXPECT_TRUE(base::PathExists(path)) << path.LossyDisplayName();
   std::string source;
@@ -45,7 +51,7 @@ void RunTestFromFile(const base::FilePath& path) {
   v8::TryCatch try_catch;
   runner.Run(Script::New(gin::StringToV8(isolate, source)));
 
-  EXPECT_FALSE(try_catch.HasCaught());
+  EXPECT_FALSE(try_catch.HasCaught()) << GetExceptionInfo(try_catch);
 }
 
 void RunTest(std::string test) {
@@ -64,6 +70,10 @@ TEST(Harness, mojo_unittests_js) {
   RunTest("mojo_unittests.js");
 }
 
+TEST(Harness, core_unittests_js) {
+  RunTest("core_unittests.js");
+}
+
 }  // namespace
 }  // namespace js
 }  // namespace mojo