[Win] CustomFrameView::IconSize() should return the value in dip unit

CustomFrameView::IconSize() returns the size of the window icon. On Windows,
the value is obtained from GetSystemMetrics(SM_CYSMICON) call, but the problem
is that the value returned is in pixel, not in dip. This leads to a wrong sized
window icon if an user is using a higher scale ratio. This CL replaces
GetSystemMetrics() with display::win::GetSystemMetricsInDIP() to fix this.

BUG=631488
TEST=See the bug page for the reproduce steps

Review-Url: https://codereview.chromium.org/2190593002
Cr-Commit-Position: refs/heads/master@{#408290}

ui/views/window/custom_frame_view.cc

@@ -31,6 +31,10 @@
 #include "ui/views/window/window_resources.h"
 #include "ui/views/window/window_shape.h"
 
+#if defined(OS_WIN)
+#include "ui/display/win/dpi.h"
+#endif
+
 namespace views {
 
 namespace {
@@ -304,7 +308,7 @@ int CustomFrameView::IconSize() const {
 #if defined(OS_WIN)
   // This metric scales up if either the titlebar height or the titlebar font
   // size are increased.
-  return GetSystemMetrics(SM_CYSMICON);
+  return display::win::GetSystemMetricsInDIP(SM_CYSMICON);
 #else
   return std::max(GetTitleFontList().GetHeight(), kIconMinimumSize);
 #endif