Allow multiple dart <script> tags in .sky files

sky/engine/core/app/AbstractModule.cpp

Index: sky/engine/core/app/AbstractModule.cpp
diff --git a/sky/engine/core/app/AbstractModule.cpp b/sky/engine/core/app/AbstractModule.cpp
index 3cd17cf515565793e5c7b103edb8e843b2adce52..cc525fbfe0e297a296876a6ed8f4a29e474dcaca 100644
--- a/sky/engine/core/app/AbstractModule.cpp
+++ b/sky/engine/core/app/AbstractModule.cpp
@@ -22,6 +22,20 @@ AbstractModule::~AbstractModule() {
   document_->setModule(nullptr);
 }
 
+void AbstractModule::AddLibrary(RefPtr<DartValue> library,
+                                TextPosition position) {
+  libraries_.append(LibraryEntry(library, position));
+}
+
+String AbstractModule::UrlForLibraryAt(TextPosition position) {
+  // TODO(eseidel): This could produce invalid urls?
+  // TODO(abarth): Mangle these library names to they're not predictable.
+  // Otherwise you could 'import url.sky' in dart and it could magically work!
+  int line = position.m_line.zeroBasedInt();
+  int column = position.m_column.zeroBasedInt();
+  return url() + String::format("#l%d,c%d", line, column);
+}
+
 ExecutionContext* AbstractModule::executionContext() const {
   return ContextLifecycleObserver::executionContext();
 }