[Extensions] Fix typos in chrome.test.sendMessage() doc

Bug: None
Change-Id: I5ef5990cfcf08aea0776f44365963719bd6a44e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2323684
Commit-Queue: Frédéric Wang <fwang@igalia.com>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792359}

extensions/docs/extension_tests.md

@@ -151,10 +151,10 @@ between events.  This class is only useful in browser tests.
 IN_PROC_BROWSER_TEST_F(...) {
   LoadExtension(...);
   GURL url = GetASpecialURL();
-  ExtensionTestMessageListener listener("clicked", /*will_reply*/=true);
+  ExtensionTestMessageListener listener("clicked", /*will_reply=*/true);
   ClickAction();
   ASSERT_TRUE(listener.WaitUntilSatisfied());
-  listener.reply(url.spec());
+  listener.Reply(url.spec());
   ...
 }
 ```

extensions/docs/testing_api.md

@@ -343,10 +343,10 @@ used with [ExtensionTestMessageListener] on the C++ side.
 IN_PROC_BROWSER_TEST_F(...) {
   LoadExtension(...);
   GURL url = GetASpecialURL();
-  ExtensionTestMessageListener listener("clicked", /*will_reply*/=true);
+  ExtensionTestMessageListener listener("clicked", /*will_reply=*/true);
   ClickAction();
   ASSERT_TRUE(listener.WaitUntilSatisfied());
-  listener.reply(url.spec());
+  listener.Reply(url.spec());
   ...
 }
 ```