Move allocate instance id to chrome/.

chrome/test/data/extensions/platform_apps/web_view/shim/main.js

Index: chrome/test/data/extensions/platform_apps/web_view/shim/main.js
diff --git a/chrome/test/data/extensions/platform_apps/web_view/shim/main.js b/chrome/test/data/extensions/platform_apps/web_view/shim/main.js
index da33baca2e1bf14f59da153d7aeeb430a6a6def0..ab41060523996fc66076a9a1fc67f01ce21ea02e 100644
--- a/chrome/test/data/extensions/platform_apps/web_view/shim/main.js
+++ b/chrome/test/data/extensions/platform_apps/web_view/shim/main.js
@@ -579,7 +579,8 @@ function testCannotMutateEventName() {
 // been set raises an exception.
 function testPartitionRaisesException() {
   var webview = document.createElement('webview');
-  webview.setAttribute('partition', arguments.callee.name);
+  var partitionAttribute = arguments.callee.name;
+  webview.setAttribute('partition', partitionAttribute);
   webview.setAttribute('src', 'data:text/html,trigger navigation');
   document.body.appendChild(webview);
   setTimeout(function() {
@@ -587,6 +588,7 @@ function testPartitionRaisesException() {
       webview.partition = 'illegal';
       embedder.test.fail();
     } catch (e) {
+      embedder.test.assertEq(partitionAttribute, webview.partition);
       embedder.test.succeed();
     }
   }, 0);