godoc: restore toy selection to playground widget

Fixes #4225.

R=golang-dev
CC=golang-dev
https://golang.org/cl/6640054

doc/play/playground.js

@@ -3,13 +3,14 @@
 // license that can be found in the LICENSE file.
 
 // opts is an object with these keys
-// 	codeEl - code editor element
-// 	outputEl - program output element
+//	codeEl - code editor element
+//	outputEl - program output element
 //	runEl - run button element
-// 	fmtEl - fmt button element (optional)
-// 	shareEl - share button element (optional)
-// 	shareURLEl - share URL text input element (optional)
-// 	shareRedirect - base URL to redirect to on share (optional)
+//	fmtEl - fmt button element (optional)
+//	shareEl - share button element (optional)
+//	shareURLEl - share URL text input element (optional)
+//	shareRedirect - base URL to redirect to on share (optional)
+//	toysEl - toys select element (optional)
 //	enableHistory - enable using HTML5 history API (optional)
 function playground(opts) {
 	var code = $(opts['codeEl']);
@@ -226,4 +227,21 @@ function playground(opts) {
 			});
 		});
 	}
+
+	if (opts['toysEl'] != null) {
+		$(opts['toysEl']).bind('change', function() {
+			var toy = $(this).val();
+			$.ajax("/doc/play/"+toy, {
+				processData: false,
+				type: "GET",
+				complete: function(xhr) {
+					if (xhr.status != 200) {
+						alert("Server error; try again.")
+						return;
+					}
+					setBody(xhr.responseText);
+				}
+			});
+		});
+	}
 }

doc/root.html

@@ -85,7 +85,6 @@ Linux, Mac OS X, Windows, and more.
 <div style="clear: both;"></div>
 
 <script type="text/javascript" src="https://www.google.com/jsapi"></script>
-<script type="text/javascript" src="/doc/play/playground.js"></script>
 <script type="text/javascript">
 google.load("feeds", "1");
 
@@ -122,7 +121,6 @@ function init() {
 
 	// Set up playground.
 	playground({
-		"simple":        true,
 		"codeEl":        "#learn .code",
 		"outputEl":      "#learn .output",
 		"runEl":         "#learn .run",