Switch to LayoutThemeMobile when emulating mobile device in DevTools.

third_party/WebKit/Source/core/style/ComputedStyle.h

Index: third_party/WebKit/Source/core/style/ComputedStyle.h
diff --git a/third_party/WebKit/Source/core/style/ComputedStyle.h b/third_party/WebKit/Source/core/style/ComputedStyle.h
index b5e0ba7fd68970370f59779d9a81aaca9fae6b05..5cbc56120724506c90b259d1a37de5bba081f0b9 100644
--- a/third_party/WebKit/Source/core/style/ComputedStyle.h
+++ b/third_party/WebKit/Source/core/style/ComputedStyle.h
@@ -356,17 +356,19 @@ private:
     ALWAYS_INLINE ComputedStyle(const ComputedStyle&);
 
     static PassRefPtr<ComputedStyle> createInitialStyle();
-    static inline ComputedStyle* initialStyle()
+    static inline ComputedStyle* initialStyle() { return *initialStylePointer(); }
+    static inline ComputedStyle** initialStylePointer()
     {
         LEAK_SANITIZER_DISABLED_SCOPE;
         DEFINE_STATIC_REF(ComputedStyle, s_initialStyle, (ComputedStyle::createInitialStyle()));
-        return s_initialStyle;
+        return &s_initialStyle;
     }
 
 public:
     static PassRefPtr<ComputedStyle> create();
     static PassRefPtr<ComputedStyle> createAnonymousStyleWithDisplay(const ComputedStyle& parentStyle, EDisplay);
     static PassRefPtr<ComputedStyle> clone(const ComputedStyle&);
+    static void clearInitialStyle();
 
     // Computes how the style change should be propagated down the tree.
     static StyleRecalcChange stylePropagationDiff(const ComputedStyle* oldStyle, const ComputedStyle* newStyle);