Adds a new dependency event that is emitted when dependency checker is

about to start. Adds ability to examine classes from generators.

teavm-core/src/main/java/org/teavm/dependency/DependencyChecker.java

@@ -89,6 +89,12 @@ public class DependencyChecker implements DependencyInformation {
         listeners.add(listener);
     }
 
+    public void startListeners() {
+        for (DependencyListener listener : listeners) {
+            listener.started(this);
+        }
+    }
+
     public void addEntryPoint(MethodReference methodRef, String... argumentTypes) {
         ValueType[] parameters = methodRef.getDescriptor().getParameterTypes();
         if (parameters.length != argumentTypes.length) {

teavm-core/src/main/java/org/teavm/dependency/DependencyListener.java

@@ -23,6 +23,8 @@ import org.teavm.model.MethodReference;
  * @author Alexey Andreev
  */
 public interface DependencyListener {
+    void started(DependencyChecker dependencyChecker);
+
     void classAchieved(DependencyChecker dependencyChecker, String className);
 
     void methodAchieved(DependencyChecker dependencyChecker, MethodReference method);

teavm-core/src/main/java/org/teavm/javascript/JavascriptBuilder.java

@@ -112,6 +112,7 @@ public class JavascriptBuilder implements JavascriptBuilderHost {
         SourceWriterBuilder builder = new SourceWriterBuilder(naming);
         builder.setMinified(minifying);
         SourceWriter sourceWriter = builder.build(writer);
+        dependencyChecker.startListeners();
         dependencyChecker.attachMethodGraph(new MethodReference("java.lang.Class", new MethodDescriptor("createNew",
                 ValueType.object("java.lang.Class"))));
         dependencyChecker.attachMethodGraph(new MethodReference("java.lang.String", new MethodDescriptor("<init>",

teavm-core/src/main/java/org/teavm/javascript/Renderer.java

@@ -373,6 +373,11 @@ public class Renderer implements ExprVisitor, StatementVisitor {
         public String getParameterName(int index) {
             return variableName(index);
         }
+
+        @Override
+        public ClassReaderSource getClassSource() {
+            return classSource;
+        }
     }
 
     @Override

teavm-core/src/main/java/org/teavm/javascript/ni/GeneratorContext.java

@@ -15,10 +15,14 @@
  */
 package org.teavm.javascript.ni;
 
+import org.teavm.model.ClassReaderSource;
+
 /**
  *
  * @author Alexey Andreev <konsoletyper@gmail.com>
  */
 public interface GeneratorContext {
     String getParameterName(int index);
+
+    ClassReaderSource getClassSource();
 }