Change snasphotting API to take in a bounds Rect

chrome/test/data/gpu/webgl_teapot/teapot_files/demo.js

Index: chrome/test/data/gpu/webgl_teapot/teapot_files/demo.js
diff --git a/chrome/test/data/gpu/webgl_teapot/teapot_files/demo.js b/chrome/test/data/gpu/webgl_teapot/teapot_files/demo.js
index fd45ee9c4d7508ae7a91099dc4a3407e6e292d54..7a982e76cee13e655e4a7548804ab55b0a4b662f 100644
--- a/chrome/test/data/gpu/webgl_teapot/teapot_files/demo.js
+++ b/chrome/test/data/gpu/webgl_teapot/teapot_files/demo.js
@@ -386,7 +386,12 @@ function loadCubeMap(base, suffix) {
 
 function waitForFinish() {
   if (g_pendingTextureLoads == 0) {
-    domAutomationController.setAutomationId(1);
-    domAutomationController.send("ok");
+    var epilogue = document.createElement("script");
+    epilogue.onload = function() {
+      domAutomationController.setAutomationId(1);
+      domAutomationController.send("ok");
+    }
+    epilogue.src = "./teapot_files/epilogue.js";
+    document.body.appendChild(epilogue);
   }
 }