win: Add "direct-write" option for BrowserWindow.

For atom/atom#3540.

atom/browser/native_window.cc

@@ -41,6 +41,7 @@
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/render_widget_host_view.h"
+#include "content/public/common/content_switches.h"
 #include "content/public/common/renderer_preferences.h"
 #include "content/public/common/user_agent.h"
 #include "ipc/ipc_message_macros.h"
@@ -351,9 +352,15 @@ void NativeWindow::AppendExtraCommandLineSwitches(
   if (web_preferences_.IsEmpty())
     return;
 
+  bool b;
+#if defined(OS_WIN)
+  // Check if DirectWrite is disabled.
+  if (web_preferences_.Get(switches::kDirectWrite, &b) && !b)
+    command_line->AppendSwitch(::switches::kDisableDirectWrite);
+#endif
+
   // This set of options are not availabe in WebPreferences, so we have to pass
   // them via command line and enable them in renderer procss.
-  bool b;
   for (size_t i = 0; i < arraysize(kWebRuntimeFeatures); ++i) {
     const char* feature = kWebRuntimeFeatures[i];
     if (web_preferences_.Get(feature, &b))

atom/common/options_switches.cc

@@ -57,6 +57,9 @@ const char kEnableLargerThanScreen[] = "enable-larger-than-screen";
 // Forces to use dark theme on Linux.
 const char kDarkTheme[] = "dark-theme";
 
+// Enable DirectWrite on Windows.
+const char kDirectWrite[] = "direct-write";
+
 // Web runtime features.
 const char kExperimentalFeatures[]       = "experimental-features";
 const char kExperimentalCanvasFeatures[] = "experimental-canvas-features";

atom/common/options_switches.h

@@ -35,6 +35,7 @@ extern const char kZoomFactor[];
 extern const char kAutoHideMenuBar[];
 extern const char kEnableLargerThanScreen[];
 extern const char kDarkTheme[];
+extern const char kDirectWrite[];
 
 extern const char kExperimentalFeatures[];
 extern const char kExperimentalCanvasFeatures[];

docs/api/browser-window.md

@@ -86,6 +86,8 @@ normal browsers, see [Web Security](web-security.md) for more.
     * `overlay-scrollbars` Boolean
     * `overlay-fullscreen-video` Boolean
     * `shared-worker` Boolean
+    * `direct-write` Boolean - Whether the DirectWrite font rendering system on
+       Windows is enabled
 
 Creates a new `BrowserWindow` with native properties set by the `options`.
 Usually you only need to set the `width` and `height`, other properties will