Partial implementation of CSSVariablesMap for CSS Variables CSSOM

Source/core/css/CSSVariablesMap.idl

Index: Source/core/css/CSSVariablesMap.idl
diff --git a/Source/core/css/CSSVariablesMap.idl b/Source/core/css/CSSVariablesMap.idl
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index 0000000000000000000000000000000000000000..1ec63d908ba4466a3139f5ddeece81a8a8dd73b5
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+/*
+ * Copyright (C) 2013 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+interface CSSVariablesMap {
+    readonly attribute unsigned long size;
+    DOMString get(DOMString name);

[arv (Not doing code reviews), 2013/07/01 13:59:46]

This needs to return undefined for non existing keys.

[TreatReturnedNullStringAs=Undefined] DOMString get(DOMString name);

[alancutter (OOO until 2018), 2013/07/02 00:27:47]

The get() method is defined as returning the value of getPropertyValue() on the
CSSStyleDeclaration which returns the empty string for unset properties.
http://www.w3.org/TR/DOM-Level-2-Style/css.html#CSS-CSSStyleDeclaration

[arv (Not doing code reviews), 2013/07/02 13:20:57]

If we are striving to quack like a Map we should return undefined. Can the spec
for CSSVariableMap be fixed?

+    boolean has(DOMString name);
+    [RaisesException] void set(DOMString name, DOMString value);
+    [ImplementedAs=deleteImpl] boolean delete(DOMString name);
+    [RaisesException] void clear();
+};