Make WebView work for external displays (over Presentations).

ui/snapshot/snapshot_android.cc

Index: ui/snapshot/snapshot_android.cc
diff --git a/ui/snapshot/snapshot_android.cc b/ui/snapshot/snapshot_android.cc
index 433d0f7f439f13721e3bfacaae454c47c2a411e5..8af02e299ed42572d964f9bbe268fdb91a8dcd8d 100644
--- a/ui/snapshot/snapshot_android.cc
+++ b/ui/snapshot/snapshot_android.cc
@@ -39,9 +39,11 @@ static void MakeAsyncCopyRequest(
   scoped_ptr<cc::CopyOutputRequest> request =
       cc::CopyOutputRequest::CreateBitmapRequest(callback);
 
-  const gfx::Display& display =
-      gfx::Screen::GetNativeScreen()->GetPrimaryDisplay();
-  float device_scale_factor = display.device_scale_factor();
+  float device_scale_factor =
+      gfx::Display::HasForceDeviceScaleFactor()
+          ? gfx::Display::GetForcedDeviceScaleFactor()
+          : window->GetDeviceDisplayInfo().GetDIPScale();
+
   gfx::Rect source_rect_in_pixel =
       gfx::ToEnclosingRect(gfx::ScaleRect(source_rect, device_scale_factor));