Fix Jumplist favicons to have high resolution in HDPI Windows displays

ui/display/win/screen_win.cc

Index: ui/display/win/screen_win.cc
diff --git a/ui/display/win/screen_win.cc b/ui/display/win/screen_win.cc
index 0ba4da99f9c2f521ade885f1997ac608cd8fbdc3..aefa7482ee19649035a6b26250bb96ca630aadb4 100644
--- a/ui/display/win/screen_win.cc
+++ b/ui/display/win/screen_win.cc
@@ -351,6 +351,18 @@ float ScreenWin::GetScaleFactorForHWND(HWND hwnd) {
   return screen_win_display.display().device_scale_factor();
 }
 
+// static
+float ScreenWin::GetLargestDeviceScaleFactor() {

[sky, 2017/02/02 22:41:16]

This function is only needed in one place, can you move it there? The code
calling this can get all the displays and iterate over it there, right?

[chengx, 2017/02/03 01:51:13]

Sure. Will make the code local to jumplist.

+  float scale = 1.0;
+  if (!g_screen_win_instance)
+    return scale;
+  std::vector<Display> displays(g_screen_win_instance->GetAllDisplays());
+  for (size_t i = 0; i < displays.size(); i++) {

[sky, 2017/02/02 22:41:16]

no {}, also, I would use enhanced for loop

[chengx, 2017/02/03 01:51:13]

Done.

+    scale = std::max(scale, displays[i].device_scale_factor());
+  }
+  return scale;
+}
+
 HWND ScreenWin::GetHWNDFromNativeView(gfx::NativeView window) const {
   NOTREACHED();
   return nullptr;