Resolve URLs passed on the command line relative to the CWD.

This will make it easier to pass arbitrary files to mojo_shell for testing.

BUG=401761
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/873253003
diff --git a/shell/command_line_util.h b/shell/command_line_util.h
index 116f03c..7ab7463 100644
--- a/shell/command_line_util.h
+++ b/shell/command_line_util.h
@@ -20,7 +20,8 @@
 // arguments are specified they will be available when the Mojo application
 // is initialized. This returns the mojo_app_url, and set args to the list of
 // arguments.
-GURL GetAppURLAndArgs(const std::string& app_url_and_args,
+GURL GetAppURLAndArgs(Context* context,
+                      const std::string& app_url_and_args,
                       std::vector<std::string>* args);
 
 // Apply arguments for an application from a line with the following format: