Show custom properties in the computed style pane of the inspector.

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

Index: third_party/WebKit/Source/core/style/StyleVariableData.h
diff --git a/third_party/WebKit/Source/core/style/StyleVariableData.h b/third_party/WebKit/Source/core/style/StyleVariableData.h
index 1c7d94143fdd76c2933c9cc3cdd67d1eae27d91b..de53f2b5f393b19d3d0a6c7b2c476d4a88db5210 100644
--- a/third_party/WebKit/Source/core/style/StyleVariableData.h
+++ b/third_party/WebKit/Source/core/style/StyleVariableData.h
@@ -20,6 +20,8 @@ public:
     void setVariable(const AtomicString& name, PassRefPtr<CSSVariableData> value) { m_data.set(name, value); }
     CSSVariableData* getVariable(const AtomicString& name) const { return m_data.get(name); }
     void removeVariable(const AtomicString& name) { return m_data.remove(name); }
+
+    const HashMap<AtomicString, RefPtr<CSSVariableData>>* getVariables() const { return &m_data; }
 private:
     StyleVariableData() = default;
     StyleVariableData(const StyleVariableData& other) : RefCounted<StyleVariableData>(), m_data(other.m_data) { }