Update Activation and Deactivation behaviors (w3c#61)

Currently the `activate/deactivate the EditContext` steps are empty stubs.

"Activating" an EditContext doesn't need to do anything, so remove that one.

Deactivating an EditContext should stop composition for that EditContext and fire `compositionend` if there was a composition.

Note, there's a bug where we have no other mechanism to end an EditContext's composition. [Update the EditContext](https://w3c.github.io/edit-context/#update-the-editcontext) will be updated to handle those cases in a separate PR.

index.html

@@ -650,12 +650,11 @@ <h3>Extensions to the HTMLElement interface</h3>
  </ol>
  </li>
  <li>Set [=this=]'s internal [[\EditContext]] slot to be |editContext|.</li>
- <li>If |oldEditContext| is not null and |oldEditContext| is the [=this=]'s
- <a href="https://dom.spec.whatwg.org/#concept-node-document">node document</a>'s [=active EditContext=], then:
- <ol>
- <li>Run the steps to [=deactivate an EditContext=] with |oldEditContext|.</li>
- <li>If |editContext| is not null, run the steps to [=activate an EditContext=] with |editContext|.</li>
- </ol>
+ <li>
+ If |oldEditContext| is not null and |oldEditContext| is [=this=]'s
+ <a href="https://dom.spec.whatwg.org/#concept-node-document">node document</a>'s
+ [=active EditContext=], then run the steps to [=deactivate an EditContext=]
+ with |oldEditContext|.
  </li>
  </ol>
  </div><!-- algorithm -->
@@ -724,7 +723,6 @@ <h4><dfn>Update the Text Edit Context</dfn></h4>
  <li>If |oldActiveEditContext| is not null, then run the steps to [=deactivate an EditContext=] given |oldActiveEditContext|.</li>
  <li>If |newActiveEditContext| is not null, then:
  <ol>
- <li>Run the steps to [=activate an EditContext=] given |newActiveEditContext|.</li>
  <li>Update the [=Text Edit Context=]'s [=text state=] to match the values in |editContext|'s [=text state=].</li>
  </ol>
  </li>
@@ -805,32 +803,20 @@ <h4><dfn>Dispatch character bounds update event</dfn></h4>
 </ol>
 </div><!-- algorithm -->
 
-<h4><dfn>Activate an EditContext</dfn></h4>
-<div class="algorithm">
- <dl>
- <dt>Input</dt>
- <dd>|this| an {{EditContext}}</dd>
- <dt>Output</dt>
- <dd>None</dd>
- </dl>
- <ol>
- <li>
- <div class="note">Add details</div>
- </li>
- </ol>
-</div><!-- algorithm -->
-
 <h4><dfn>Deactivate an EditContext</dfn></h4>
 <div class="algorithm">
  <dl>
  <dt>Input</dt>
- <dd>|this| an {{EditContext}}</dd>
+ <dd>|editContext|, an {{EditContext}}</dd>
  <dt>Output</dt>
  <dd>None</dd>
  </dl>
  <ol>
+ <li>Set |editContext|'s [=is composing=] to false.</li>
  <li>
- <div class="note">Add details</div>
+ [=Fire an event=] named
+ <a href="https://w3c.github.io/uievents/#event-type-compositionstart">compositionend</a>
+ at |editContext| using {{CompositionEvent}}.
  </li>
  </ol>
 </div><!-- algorithm -->