Initialize command line arguments for Mojo apptests.

mojo/shell/context.cc

Index: mojo/shell/context.cc
diff --git a/mojo/shell/context.cc b/mojo/shell/context.cc
index fc56476f819ea3392cb56a58ddb5b08aa9d4b71b..032d392ea154cee84708737bda5bd13b2a5431ce 100644
--- a/mojo/shell/context.cc
+++ b/mojo/shell/context.cc
@@ -84,6 +84,26 @@ bool ConfigureURLMappings(const base::CommandLine& command_line,
     resolver->AddOriginMapping(GURL(origin_mapping.origin),
                                GURL(origin_mapping.base_url));
 
+  // TODO(msw): Ensure URL mappings are only used for testing??? 
+  if (command_line.HasSwitch(switches::kURLMappings)) {
+    const std::string mappings =
+        command_line.GetSwitchValueASCII(switches::kURLMappings);
+
+    base::StringPairs pairs;
+    if (!base::SplitStringIntoKeyValuePairs(mappings, '=', ',', &pairs))
+      return false;
+    using StringPair = std::pair<std::string, std::string>;
+    for (const StringPair& pair : pairs) {
+      const GURL from(pair.first);
+      const GURL to = context->ResolveCommandLineURL(pair.second);
+      //printf("MSW mapping: %s -> %s\n", from.possibly_invalid_spec().c_str(), to.possibly_invalid_spec().c_str());
+      if (!from.is_valid() || !to.is_valid())
+        return false;
+
+      resolver->AddURLMapping(from, to);
+    }
+  }
+
   return true;
 }