Switch to LayoutThemeMobile when emulating mobile device in DevTools.

third_party/WebKit/Source/core/paint/ThemePainterMac.mm

Index: third_party/WebKit/Source/core/paint/ThemePainterMac.mm
diff --git a/third_party/WebKit/Source/core/paint/ThemePainterMac.mm b/third_party/WebKit/Source/core/paint/ThemePainterMac.mm
index 8c9157caf73cbb8c4a1c5b1306d5a68b497593f6..7424cb6ea3b01b25e1cf8730a5ac519210f490c3 100644
--- a/third_party/WebKit/Source/core/paint/ThemePainterMac.mm
+++ b/third_party/WebKit/Source/core/paint/ThemePainterMac.mm
@@ -50,6 +50,12 @@ void _NSDrawCarbonThemeListBox(NSRect frame, BOOL enabled, BOOL flipped, BOOL al
 
 namespace blink {
 
+ThemePainterMac::ThemePainterMac(LayoutThemeMac& layoutTheme, Theme* platformTheme)
+    : ThemePainter(platformTheme)
+    , m_layoutTheme(layoutTheme)
+{
+}
+
 bool ThemePainterMac::paintTextField(const LayoutObject& o, const PaintInfo& paintInfo, const IntRect& r)
 {
     LocalCurrentGraphicsContext localContext(paintInfo.context, &paintInfo.cullRect().m_rect, r);