Reapply "Create an app snapshot of the Dart front end."

runtime/vm/kernel_isolate.cc

Index: runtime/vm/kernel_isolate.cc
diff --git a/runtime/vm/kernel_isolate.cc b/runtime/vm/kernel_isolate.cc
index 8d682ab2cd786aa1a299925801b3a6d94dce674e..9cf20057b1f3d57445e8bf10c790d6f405b4710e 100644
--- a/runtime/vm/kernel_isolate.cc
+++ b/runtime/vm/kernel_isolate.cc
@@ -154,7 +154,7 @@ class RunKernelTask : public ThreadPool::Task {
       return false;
     }
     ASSERT(!root_library.IsNull());
-    const String& entry_name = String::Handle(Z, String::New("main"));
+    const String& entry_name = String::Handle(Z, String::New("start"));
     ASSERT(!entry_name.IsNull());
     const Function& entry = Function::Handle(
         Z, root_library.LookupFunctionAllowPrivate(entry_name));