Add Kernel Isolate

runtime/bin/loader.cc

Index: runtime/bin/loader.cc
diff --git a/runtime/bin/loader.cc b/runtime/bin/loader.cc
index d0a95e259d1ba412f5711041a3326516b02ff475..29d0cf42c873787a4a8973029e784cb38ab94575 100644
--- a/runtime/bin/loader.cc
+++ b/runtime/bin/loader.cc
@@ -206,6 +206,24 @@ void Loader::SendRequest(Dart_LibraryTag tag,
 }
 
 
+// Forward a request from the tag handler to the kernel isolate.
+// [ tag, send port, url ]
+void Loader::SendKernelRequest(Dart_LibraryTag tag, Dart_Handle url) {
+  // This port delivers loading messages to the Kernel isolate.
+  Dart_Port kernel_port = Dart_KernelPort();
+  ASSERT(kernel_port != ILLEGAL_PORT);
+
+  Dart_Handle request = Dart_NewList(3);
+  Dart_ListSetAt(request, 0, Dart_NewInteger(tag));
+  Dart_ListSetAt(request, 1, Dart_NewSendPort(port_));
+  Dart_ListSetAt(request, 2, url);
+  if (Dart_Post(kernel_port, request)) {
+    MonitorLocker ml(monitor_);
+    pending_operations_++;
+  }
+}
+
+
 void Loader::QueueMessage(Dart_CObject* message) {
   MonitorLocker ml(monitor_);
   if (results_length_ == results_capacity_) {
@@ -625,9 +643,13 @@ Dart_Handle Loader::LibraryTagHandler(Dart_LibraryTag tag,
   if (DartUtils::IsDartExtensionSchemeURL(url_string)) {
     loader->SendImportExtensionRequest(url, Dart_LibraryUrl(library));
   } else {
-    loader->SendRequest(tag, url, (library != Dart_Null())
-                                      ? Dart_LibraryUrl(library)
-                                      : Dart_Null());
+    if (Dart_KernelIsolateIsRunning()) {

[siva, 2016/12/05 22:36:10]

You could potentially turn this into

if (use_dart_frontend) {
  if (Dart_KernelIsolateRunning()) {
    loader->SendKernelRequest(tag, url);
  } else {
    return Dart_NewApiError("Cannot load sources as kernel isolate is not
running");
  }

to ensure that we don't run code through the regular loading process when -dfe
is specified on the command line.

Please feel free to ignore this comment if the plan is abort execution when the
kernel isolate fails to start during the initialize process.

[hausner, 2016/12/06 19:10:28]

This doesn't work because the Kernel isolate code is loaded through this code
path as well. In that case, the KernelIsolate isn't running of course, and we'd
report the error.

+      loader->SendKernelRequest(tag, url);
+    } else {
+      loader->SendRequest(tag, url, (library != Dart_Null())
+                                        ? Dart_LibraryUrl(library)
+                                        : Dart_Null());
+    }
   }