Revert of Remove remote tree host and some related input and metro_driver code

win8/delegate_execute/command_execute_impl.cc

Index: win8/delegate_execute/command_execute_impl.cc
diff --git a/win8/delegate_execute/command_execute_impl.cc b/win8/delegate_execute/command_execute_impl.cc
index 2711336bff109e499c3a4d6c90b1ab677affcc05..236f86271560ff1c1cf3da0e2a8ada3a628aed65 100644
--- a/win8/delegate_execute/command_execute_impl.cc
+++ b/win8/delegate_execute/command_execute_impl.cc
@@ -32,6 +32,7 @@
 #include "ui/gfx/win/dpi.h"
 #include "win8/delegate_execute/chrome_util.h"
 #include "win8/delegate_execute/delegate_execute_util.h"
+#include "win8/viewer/metro_viewer_constants.h"
 
 namespace {
 // Helper function to retrieve the url from IShellItem interface passed in.
@@ -218,8 +219,18 @@
     return E_FAIL;
   }
 
-  // TODO(scottmg): Can all go eventually https://crbug.com/558054.
-  *pahe = AHE_DESKTOP;
+  EC_HOST_UI_MODE mode = GetLaunchMode();
+  *pahe = (mode == ECHUIM_DESKTOP) ? AHE_DESKTOP : AHE_IMMERSIVE;
+
+  // If we're going to return AHE_IMMERSIVE, then both the browser process and
+  // the metro viewer need to launch and connect before the user can start
+  // browsing.  However we must not launch the metro viewer until we get a
+  // call to CommandExecuteImpl::Execute().  If we wait until then to launch
+  // the browser process as well, it will appear laggy while they connect to
+  // each other, so we pre-launch the browser process now.
+  if (*pahe == AHE_IMMERSIVE && verb_ != win8::kMetroViewerConnectVerb) {
+    LaunchChromeBrowserProcess();
+  }
   return S_OK;
 }