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 f6bb6ded053ce0c9a4185c396cd962e1bb0fdba9..1b47cc815d50d203a06af5677eee363ac48743d3 100644
--- a/mojo/shell/desktop/launcher_process.cc
+++ b/mojo/shell/desktop/launcher_process.cc
@@ -15,7 +15,6 @@
 #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"
 
@@ -23,29 +22,6 @@ 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;
 
@@ -99,28 +75,28 @@ void StopTracingAndFlushToDisk() {
   flush_complete_event.Wait();
 }
 
+void StartApp(mojo::shell::Context* context) {
+  // If a mojo app isn't specified (i.e. for an apptest), run the mojo shell's

[msw, 2015/04/13 18:15:46]

I suggested this to Ben and Scott, but Ben thought that this might not work if
we wanted to specify sites/apps on the commandline for mandoline to run and
still be embedded within the window_manager... We hadn't considered checking for
the mojo scheme, so this may be okay, but Ben suggested using a test commandline
switch, so I started with something like line 148 of
<https://codereview.chromium.org/1070463003/diff/20001/mojo/shell/desktop/laun...>,
or maybe we'd want --test-app=<app name/URL>. Also, this removes the ability to
launch multiple apps, but I'm not sure if that's worth saving...

[jam, 2015/04/13 18:36:17]

I'm curious what's lacking with specifying the test app (i.e. current approach)?
I don't see why we need that for a mandoline..

[msw, 2015/04/13 19:58:32]

The problem with the approach when this CL first landed, was that when trying to
run any apptest, we connect to window_manager and open a native window. That
connection is unnecessary (and a performance burden), and causes the test to
hang after running (we'd need to explicitly close the window).

I think the trouble with inferring whether or not to connect to window_manager
(as in this patch set), is that some command lines would be ambiguous: maybe "$
mojo_shell mojo:foo" should embed the app within the window_manager, while "$
mojo_shell mojo:foo_apptests" should simply run the tests in a headless manner.
Perhaps Ben can more clearly explain the need for an explicit apptest switch...
We might not need it, at least for now... It can be added later as needed.

[Ben Goodger (Google), 2015/04/13 20:13:30]

I'm OK with not supporting running multiple apps unless that is needed for
testing.

IMO running multiple apps was always a bit dubious. There should be one app that
is the "orchestrator" that manages the lifetimes etc. of the others.

+  // window manager.
+  GURL app_url(GURL("mojo:window_manager"));
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+  base::CommandLine::StringVector args = command_line->GetArgs();
+  for (size_t i = 0; i < args.size(); ++i) {
+    GURL possible_app(args[i]);
+    if (possible_app.SchemeIs("mojo")) {
+      app_url = possible_app;
+      break;
+    }
+  }
+
+  context->Run(app_url);
+}
+
 }  // 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(
@@ -136,7 +112,6 @@ int LauncherProcessMain(int argc, char** argv) {
   {
     base::MessageLoop message_loop;
     if (!shell_context.Init()) {
-      Usage();
       return 0;
     }
     if (g_tracing) {
@@ -145,16 +120,7 @@ int LauncherProcessMain(int argc, char** argv) {
                                    base::TimeDelta::FromSeconds(5));
     }
 
-    // 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.PostTask(FROM_HERE, base::Bind(&StartApp, &shell_context));
     message_loop.Run();
 
     // Must be called before |message_loop| is destroyed.