Pass mojo_shell args to child processes.

This allows URL(s) sent as args to be passed to the window manager. Also send --override-use-gl-with-osmesa-for-tests since it's listed on the sites page.

Review URL: https://codereview.chromium.org/1108023002

Cr-Commit-Position: refs/heads/master@{#327056}

mojo/shell/BUILD.gn

@@ -123,6 +123,7 @@ source_set("lib") {
     "//mojo/services/network/public/interfaces",
     "//mojo/shell/application_manager",
     "//mojo/services/tracing:bindings",
+    "//ui/gl",
     "//url",
   ]
 

mojo/shell/child_process_host.cc

@@ -22,6 +22,7 @@
 #include "mojo/shell/context.h"
 #include "mojo/shell/switches.h"
 #include "mojo/shell/task_runners.h"
+#include "ui/gl/gl_switches.h"
 
 namespace mojo {
 namespace shell {
@@ -97,7 +98,10 @@ void ChildProcessHost::DidStart(bool success) {
 
 bool ChildProcessHost::DoLaunch() {
   static const char* kForwardSwitches[] = {
-      switches::kTraceToConsole, switches::kV, switches::kVModule,
+      switches::kOverrideUseGLWithOSMesaForTests,
+      switches::kTraceToConsole,
+      switches::kV,
+      switches::kVModule,
   };
 
   const base::CommandLine* parent_command_line =
@@ -116,6 +120,10 @@ bool ChildProcessHost::DoLaunch() {
       child_command_line.AppendSwitch(switches::kWaitForDebugger);
   }
 
+  auto args = parent_command_line->GetArgs();
+  for (const auto& arg : args)
+    child_command_line.AppendArgNative(arg);
+
   embedder::HandlePassingInformation handle_passing_info;
   platform_channel_pair_.PrepareToPassClientHandleToChildProcess(
       &child_command_line, &handle_passing_info);