Teach SkyShell.app to run local files

Previously we defaulted to loading from URLs, but its
more common to want to load files off the local machine
on the command line.

sky/shell/mac/sky_window.mm

@@ -85,12 +85,6 @@ static inline sky::EventType EventTypeFromNSEventPhase(NSEventPhase phase) {
   self.platformView->ConnectToEngine(interface_request.Pass());
 
   base::CommandLine& command_line = *base::CommandLine::ForCurrentProcess();
-  base::CommandLine::StringVector args = command_line.GetArgs();
-  if (args.size() > 0) {
-    mojo::String string(args[0]);
-    _sky_engine->RunFromNetwork(string);
-    return;
-  }
 
   if (command_line.HasSwitch(sky::shell::switches::kSnapshot)) {
     auto snapshot = command_line.GetSwitchValueASCII(sky::shell::switches::kSnapshot);
@@ -98,9 +92,15 @@ static inline sky::EventType EventTypeFromNSEventPhase(NSEventPhase phase) {
     return;
   }
 
+  auto args = command_line.GetArgs();
+  if (args.size() > 0) {
+    _sky_engine->RunFromFile(args[0],
+        command_line.GetSwitchValueASCII(sky::shell::switches::kPackageRoot));
+    return;
+  }
+
   NSString *endpoint = self.skyInitialBundleURL;
   if (endpoint.length > 0) {
-    // Load from bundle
     mojo::String string(endpoint.UTF8String);
     _sky_engine->RunFromBundle(string);
     return;
@@ -108,7 +108,6 @@ static inline sky::EventType EventTypeFromNSEventPhase(NSEventPhase phase) {
 
   endpoint = self.skyInitialLoadURL;
   if (endpoint.length > 0) {
-    // Load from URL
     mojo::String string(endpoint.UTF8String);
     _sky_engine->RunFromNetwork(string);
     return;