Make pair iterators inherit from %IteratorPrototype%.

third_party/WebKit/Source/bindings/IDLExtendedAttributes.md

 # Blink IDL Extended Attributes
 
 [TOC]
 
 ## Introduction
 
 The main interest in extended attributes are their _semantics_: Blink implements many more extended attributes than the Web IDL standard, to specify various behavior.
 
 The authoritative list of allowed extended attributes and values is [bindings/IDLExtendedAttributes.txt](https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit/Source/bindings/IDLExtendedAttributes.txt). This is complete but not necessarily precise (there may be unused extended attributes or values), since validation is run on build, but coverage isn't checked.
 
@@ skipping 912 matching lines @@
 ```
 
 The deprecation message show on the console can be specified via the [UseCounter::deprecationMessage](https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit/Source/core/frame/UseCounter.cpp&q=UseCounter::deprecationMessage&l=615) method.
 
 ### [DoNotTestNewObject] _(m)_
 
 Summary: Does not generate a test for `[NewObject]` in the binding layer.
 
 When specified, does not generate a test for `[NewObject]`. Some implementation creates a new DOM object and its wrapper before passing through the binding layer. In that case, the generated test doesn't make sense. See Text.splitText() for example.
 
-### [Iterable] _(i)_
-
-Summary: Installs a @@iterator method.
-
-*** note
-In most cases, interfaces should use the standard `iterator<valuetype>`, `iterator<keytype,valuetype>`, `setlike<type>`, or `maplike<keytype, valuetype>` IDL declarations instead. `[Iterable]` should only be necessary for the implementation of iterators themselves.
-***
-
-When the attribute is set on an interface, the code generator installs iterator C++ method into [Symbol.iterator] slot.
-
-```webidl
-[ Iterable ] interface IterableInterface { };
-```
-
-C++ implementation:
-
-```c++
-class IterableInterface : public ScriptWrappable {
-...
-public:
-...
-    // This is called when |obj[Symbol.iterator]| is called.
-    Iterator* iterator(ScriptState*, ExceptionState&);
-};
-```
-
-JavaScript usage:
-
-```js
-var obj = ...; // obj is an IterableInterface object.
-var iter = obj[Symbol.iterator](); // IterableInterface::iterator is called.
-for (var value of obj) {
-    // Iterates over |obj|.
-}
-for (var value of iter) {
-    // Same as above.
-}
-```
-
-*** note
-Currently the code generator doesn't take care of the name conflict. Namely, it is not allowed to have "iterator" method in an iterable interface.
-***
-
 ### [Measure] _(i, m, a, c)_
 
 Summary: Measures usage of a specific feature via UseCounter.
 
 In order to measure usage of specific features, Chrome submits anonymous statistics through the Histogram recording system for users who opt-in to sharing usage statistics. This extended attribute hooks up a specific feature to this measurement system.
 
 Usage: `[Measure]` can be specified on interfaces, methods, attributes, and constants. When specified on an interface usage of the constructor will be measured. The generated feature name must be added to [UseCounter::Feature](https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit/Source/core/frame/UseCounter.h&q=%22enum%20Feature%22&sq=package:chromium&type=cs&l=61) (in [core/frame/UseCounter.h](https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit/Source/core/frame/UseCounter.h)).
 
 ```webidl
 [Measure] attribute Node interestingAttribute;
@@ skipping 619 matching lines @@
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 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
 
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 THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS 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 APPLE INC. OR ITS 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.
 ***
 
 [CrossOriginProperties]: https://html.spec.whatwg.org/multipage/browsers.html#crossoriginproperties-(-o-)