Implement chrome.experimental.clipboard extension API.

chrome/common/extensions/docs/static/experimental.clipboard.html

Index: chrome/common/extensions/docs/static/experimental.clipboard.html
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--- chrome/common/extensions/docs/static/experimental.clipboard.html	(revision 0)
+++ chrome/common/extensions/docs/static/experimental.clipboard.html	(revision 0)
@@ -0,0 +1,16 @@
+<!-- BEGIN AUTHORED CONTENT -->
+<p id="classSummary">
+For information on how to use experimental APIs,
+see the <a href="experimental.html">chrome.experimental.* APIs</a> page.
+</p>
+
+<h2>Notes</h2>
+
+<p>
+For all functions exposed by this API, the argument to the callback indicates
+whether or not the event was successfully dispatched, not whether the event was
+successfully processed and handled. Most callers won't care, since a failure
+generally indicates the tab is going away.
+</p>
+
+<!-- END AUTHORED CONTENT -->