Revert of Simplify mojo_shell since it's now only used for Mandoline.

mojo/shell/desktop/launcher_process.cc

Index: mojo/shell/desktop/launcher_process.cc
diff --git a/mojo/shell/desktop/launcher_process.cc b/mojo/shell/desktop/launcher_process.cc
index 09f7fc57e60411668e04279fb751f8c8246226c2..f6bb6ded053ce0c9a4185c396cd962e1bb0fdba9 100644
--- a/mojo/shell/desktop/launcher_process.cc
+++ b/mojo/shell/desktop/launcher_process.cc
@@ -15,6 +15,7 @@
 #include "base/message_loop/message_loop.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/trace_event/trace_event.h"
+#include "mojo/shell/command_line_util.h"
 #include "mojo/shell/context.h"
 #include "mojo/shell/switches.h"
 
@@ -22,6 +23,29 @@ namespace mojo {
 namespace shell {
 namespace {
 
+void Usage() {
+  std::cerr << "Launch Mojo applications.\n";
+  std::cerr
+      << "Usage: mojo_shell"
+      << " [--" << switches::kArgsFor << "=<mojo-app>]"
+      << " [--" << switches::kContentHandlers << "=<handlers>]"
+      << " [--" << switches::kDisableCache << "]"
+      << " [--" << switches::kEnableMultiprocess << "]"
+      << " [--" << switches::kOrigin << "=<url-lib-path>]"
+      << " [--" << switches::kTraceStartup << "]"
+      << " [--" << switches::kURLMappings << "=from1=to1,from2=to2]"
+      << " [--" << switches::kPredictableAppFilenames << "]"
+      << " [--" << switches::kWaitForDebugger << "]"
+      << " <mojo-app> ...\n\n"
+      << "A <mojo-app> is a Mojo URL or a Mojo URL and arguments within "
+      << "quotes.\n"
+      << "Example: mojo_shell \"mojo:js_standalone test.js\".\n"
+      << "<url-lib-path> is searched for shared libraries named by mojo URLs.\n"
+      << "The value of <handlers> is a comma separated list like:\n"
+      << "text/html,mojo:html_viewer,"
+      << "application/javascript,mojo:js_content_handler\n";
+}
+
 // Whether we're currently tracing.
 bool g_tracing = false;
 
@@ -75,15 +99,28 @@ void StopTracingAndFlushToDisk() {
   flush_complete_event.Wait();
 }
 
-void StartWindowManager(mojo::shell::Context* context) {
-  context->Run(GURL("mojo:window_manager"));
-}
-
 }  // namespace
 
 int LauncherProcessMain(int argc, char** argv) {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
+
+  const std::set<std::string> all_switches = switches::GetAllSwitches();
+  const base::CommandLine::SwitchMap switches = command_line.GetSwitches();
+  bool found_unknown_switch = false;
+  for (const auto& s : switches) {
+    if (all_switches.find(s.first) == all_switches.end()) {
+      std::cerr << "unknown switch: " << s.first << std::endl;
+      found_unknown_switch = true;
+    }
+  }
+
+  if (found_unknown_switch || command_line.HasSwitch(switches::kHelp) ||
+      command_line.GetArgs().empty()) {
+    Usage();
+    return 0;
+  }
+
   if (command_line.HasSwitch(switches::kTraceStartup)) {
     g_tracing = true;
     base::trace_event::CategoryFilter category_filter(
@@ -99,6 +136,7 @@ int LauncherProcessMain(int argc, char** argv) {
   {
     base::MessageLoop message_loop;
     if (!shell_context.Init()) {
+      Usage();
       return 0;
     }
     if (g_tracing) {
@@ -107,8 +145,16 @@ int LauncherProcessMain(int argc, char** argv) {
                                    base::TimeDelta::FromSeconds(5));
     }
 
-    message_loop.PostTask(FROM_HERE,
-                          base::Bind(&StartWindowManager, &shell_context));
+    // The mojo_shell --args-for command-line switch is handled specially
+    // because it can appear more than once. The base::CommandLine class
+    // collapses multiple occurrences of the same switch.
+    for (int i = 1; i < argc; i++) {
+      ApplyApplicationArgs(&shell_context, argv[i]);
+    }
+
+    message_loop.PostTask(
+        FROM_HERE,
+        base::Bind(&mojo::shell::RunCommandLineApps, &shell_context));
     message_loop.Run();
 
     // Must be called before |message_loop| is destroyed.