Train ddc snapshot on itself

utils/dartdevc/BUILD.gn

Index: utils/dartdevc/BUILD.gn
diff --git a/utils/dartdevc/BUILD.gn b/utils/dartdevc/BUILD.gn
index ba51ab4eed24cb2c63a131a29e4c57baa0ded2e6..8aef61e2147a128efe2a6a2d5d89a085cd17e40d 100644
--- a/utils/dartdevc/BUILD.gn
+++ b/utils/dartdevc/BUILD.gn
@@ -11,7 +11,12 @@ application_snapshot("dartdevc") {
     rebase_path("../../sdk"),
     "--dart-sdk-summary",
     rebase_path("../../pkg/dev_compiler/lib/sdk/ddc_sdk.sum"),
-    "--help",
+    "--library-root",
+    rebase_path("../../pkg/dev_compiler/"),
+    "--unsafe-force-compile",

[Jacob, 2017/02/21 15:28:52]

random idea: can we train it on some large existing package more representative
of real world workloads instead of compiling ddc on itself?
that would allow removing the --unsafe-force-compile arguments and likely make
the training data more representative of real world workloads. For example,
train on the angular package?

+    "-o",
+    "out.js",
+    "../../pkg/dev_compiler/bin/dartdevc.dart",
   ]
   inputs = exec_script("../../tools/list_dart_files.py",
                        [ "absolute",