Load the metro driver dll at startup

chrome/app/chrome_exe_main_win.cc

Index: chrome/app/chrome_exe_main_win.cc
===================================================================
--- chrome/app/chrome_exe_main_win.cc	(revision 125893)
+++ chrome/app/chrome_exe_main_win.cc	(working copy)
@@ -13,7 +13,12 @@
 #include "content/public/common/result_codes.h"
 #include "sandbox/src/sandbox_factory.h"
 
-int APIENTRY wWinMain(HINSTANCE instance, HINSTANCE, wchar_t*, int) {
+namespace {

[darin (slow to review), 2012/03/16 21:12:57]

nit: new line after namespace open

+typedef int (*InitMetro)(LPTHREAD_START_ROUTINE thread_proc);
+// this environment variable controls the loading of the metro driver DLL.

[darin (slow to review), 2012/03/16 21:12:57]

brett-nit: "this" -> "This"

+const char* kMetroModeEnvVar = "CHROME_METRO_DLL";
+
+int RunChrome(HINSTANCE instance) {
   bool exit_now = true;
   // We restarted because of a previous crash. Ask user if we should relaunch.
   if (ShowRestartDialogIfCrashed(&exit_now)) {
@@ -36,6 +41,58 @@
   int rc = loader->Launch(instance, &sandbox_info);
   loader->RelaunchChromeBrowserWithNewCommandLineIfNeeded();
   delete loader;
-
   return rc;
 }
+
+// Helper class to manage the metro driver dll. When present in the system,
+// the main process thread needs to call InitMetro() on the dll.
+class MetroDriver {

[darin (slow to review), 2012/03/16 21:12:57]

feels like this should be in a file of its own

+ public:
+  MetroDriver() : metro_dll_(0), init_metro_fn_(NULL) {
+    if (0 != ::GetEnvironmentVariableA(kMetroModeEnvVar, NULL, 0))
+      return;
+    // We haven't tried to load the metro driver, this probably means we are the
+    // browser. Find it or not we set the environment variable because we don't
+    // want to keep trying in the child processes.
+    metro_dll_ = ::LoadLibraryA("metro_driver.dll");
+    ::SetEnvironmentVariableA(kMetroModeEnvVar, metro_dll_ ? "1" : "0");
+    if (!metro_dll_)
+      return;
+    init_metro_fn_ = reinterpret_cast<InitMetro>(
+        ::GetProcAddress(metro_dll_, "InitMetro"));
+  }
+
+  // returns true if chrome is being launched in metro. If so we should
+  // call RunInMetro(). If not then we should just run chrome as usual.
+  bool in_metro_mode() const {
+    return (init_metro_fn_ != NULL);
+  }
+
+  // Enter the metro main function, which will only return when chrome metro
+  // is closed. Once metro has initialized, the dll creates a new thread
+  // which will run|SurrogateMainThread|.
+  int RunInMetro(HINSTANCE instance) {
+    module_instance_ = instance;
+    return init_metro_fn_(&SurrogateMainThread);
+  }
+
+ private:
+  static HINSTANCE module_instance_;
+
+  static DWORD WINAPI SurrogateMainThread(void*) {
+    return RunChrome(module_instance_);
+  }
+
+  HMODULE metro_dll_;
+  InitMetro init_metro_fn_;
+};
+
+HINSTANCE MetroDriver::module_instance_;
+}  // namespace

[darin (slow to review), 2012/03/16 21:12:57]

nit: new line before namespace close

+
+int APIENTRY wWinMain(HINSTANCE instance, HINSTANCE prev, wchar_t*, int) {
+  MetroDriver metro_driver;
+  if (metro_driver.in_metro_mode())
+    return metro_driver.RunInMetro(instance);
+  return RunChrome(instance);
+}