Added a rudimentary DOM, to assist with event dispatch.

runtime/embedders/openglui/emulator/emulator_embedder.cc

Index: runtime/embedders/openglui/emulator/emulator_embedder.cc
===================================================================
--- runtime/embedders/openglui/emulator/emulator_embedder.cc	(revision 19252)
+++ runtime/embedders/openglui/emulator/emulator_embedder.cc	(working copy)
@@ -53,8 +53,8 @@
 }
 
 void keyboard(unsigned char key, int x, int y) {
-  input_handler_ptr->OnKeyEvent(kKeyDown, time(0), 0, key, 0, 0);
-  input_handler_ptr->OnKeyEvent(kKeyUp, time(0), 0, key, 0, 0);
+  input_handler_ptr->OnKeyEvent(kKeyDown, time(0), key, false, false, false, 0);
+  input_handler_ptr->OnKeyEvent(kKeyUp, time(0), key, false, false, false, 0);
   if (key == 27) {
     lifecycle_handler_ptr->Pause();
     lifecycle_handler_ptr->Deactivate();
@@ -77,6 +77,18 @@
   }
 }
 
+void mouse(int button, int state, int x, int y) {
+  if (state == GLUT_UP) {
+    input_handler_ptr->OnMotionEvent(kMotionUp, time(0), x, y);
+  } else if (state == GLUT_DOWN) {
+    input_handler_ptr->OnMotionEvent(kMotionDown, time(0), x, y);
+  }
+}
+
+void motion(int x, int y) {
+  input_handler_ptr->OnMotionEvent(kMotionMove, time(0), x, y);
+}
+
 DART_EXPORT void emulator_main(int argc, char** argv, const char* script) {
   EmulatorGraphicsHandler graphics_handler(argc, argv);
   if (argc > 0) {
@@ -102,6 +114,8 @@
   glutReshapeFunc(reshape);
   glutDisplayFunc(display);
   glutKeyboardFunc(keyboard);
+  glutMouseFunc(mouse);
+  glutMotionFunc(motion);
   lifecycle_handler_ptr->OnStart();
   lifecycle_handler_ptr->Activate();
   lifecycle_handler_ptr->Resume();