Remove 'writable:false' from webview.request's definition since false is

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 0ba8d81f4b81ffe3ffa87d3d99d7a7dd55afe502..647c3b7762a453e71069aa7327a6917c02828a7e 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
@@ -386,6 +386,11 @@ function testWebRequestAPIExistence() {
           'function',
           typeof webview.request[apiPropertiesToCheck[i]].removeRules);
     }
+
+    // Try to overwrite webview.request, shall not succeed.
+    webview.request = '123';
+    embedder.test.assertTrue(typeof webview.request !== 'string');
+
     embedder.test.succeed();
   });
   webview.setAttribute('src', 'data:text/html,webview check api');