[Extensions] Quick spelling change to existing files.

Bug: None
Change-Id: I5e5e05124668a459af71f4304918d0639f1bd75b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2463397Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Commit-Queue: Solomon Kinard <solomonkinard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#817686}

chrome/test/data/extensions/api_test/tabs/connect/test.js

@@ -100,7 +100,7 @@ chrome.test.runTests([
   },
 
   function connectToRemovedTab() {
-    // Expect a disconnect event when you connect to a non-existant tab, and
+    // Expect a disconnect event when you connect to a non-existent tab, and
     // once disconnected, expect an error while trying to post messages.
     chrome.tabs.create({}, pass(function(tab) {
       chrome.tabs.remove(tab.id, pass(function() {

chrome/test/data/extensions/api_test/webnavigation/failures/test_failures.js

@@ -199,7 +199,7 @@ onload = async function() {
     },
 
     // Navigates to a non-existent page (this test case must be last,
-    // otherwise the non-existant URL breaks tests that follow, since loading
+    // otherwise the non-existent URL breaks tests that follow, since loading
     // those test pages is seen as a non-extension -> extension URL
     // transition, which is forbidden by web_accessible_resources enforcement
     // in manifest version 2.)

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

@@ -72,8 +72,8 @@ function testAppViewWithUndefinedDataShouldSucceed(appToEmbed) {
   var appview = new AppView();
   LOG('appToEmbed  ' + appToEmbed);
   document.body.appendChild(appview);
-  // Step 1: Attempt to connect to a non-existant app.
-  LOG('attempting to connect to non-existant app.');
+  // Step 1: Attempt to connect to a non-existent app.
+  LOG('attempting to connect to non-existent app.');
   appview.connect('abc123', undefined, function(success) {
     // Make sure we fail.
     if (success) {
@@ -81,7 +81,7 @@ function testAppViewWithUndefinedDataShouldSucceed(appToEmbed) {
       embedder.test.fail();
       return;
     }
-    LOG('failed to connect to non-existant app.');
+    LOG('failed to connect to non-existent app.');
     LOG('attempting to connect to known app.');
     // Step 2: Attempt to connect to an app we know exists.
     appview.connect(appToEmbed, undefined, function(success) {

extensions/browser/extension_api_frame_id_map.h

@@ -24,7 +24,7 @@ namespace extensions {
 // following characteristics:
 // - The top-level frame has ID 0.
 // - Any child frame has a positive ID.
-// - A non-existant frame has ID -1.
+// - A non-existent frame has ID -1.
 // - They are only guaranteed to be unique within a tab.
 // - The ID does not change during the frame's lifetime and is not re-used after
 //   the frame is removed. The frame may change its current RenderFrameHost over

extensions/browser/file_reader_unittest.cc

@@ -86,7 +86,7 @@ TEST_F(FileReaderTest, BiggerFile) {
   RunBasicTest("bigfile");
 }
 
-TEST_F(FileReaderTest, NonExistantFile) {
+TEST_F(FileReaderTest, NonExistentFile) {
   base::FilePath path;
   base::PathService::Get(DIR_TEST_DATA, &path);
   std::string extension_id = crx_file::id_util::GenerateId("test");

extensions/test/data/app_view/apitest/main.js

@@ -107,7 +107,7 @@ function testAppViewWithUndefinedDataShouldSucceed(appToEmbed) {
   var appview = new AppView();
   LOG('appToEmbed  ' + appToEmbed);
   document.body.appendChild(appview);
-  // Step 1: Attempt to connect to a non-existant app (abc123).
+  // Step 1: Attempt to connect to a non-existent app (abc123).
   LOG('Attempting to connect to non-existent app.');
   appview.connect('abc123', undefined, function(success) {
     // Make sure we fail.

services/network/public/cpp/simple_url_loader_unittest.cc

@@ -1852,7 +1852,7 @@ TEST_P(SimpleURLLoaderTest, UploadFileWithRetry) {
     EXPECT_EQ(1, test_helper->download_as_stream_retries());
 }
 
-TEST_P(SimpleURLLoaderTest, UploadNonexistantFile) {
+TEST_P(SimpleURLLoaderTest, UploadNonexistentFile) {
   std::unique_ptr<SimpleLoaderTestHelper> test_helper =
       CreateHelperForURL(test_server_.GetURL("/echo"), "POST");
   // Path to a file that doesn't exist.  Start with the test directory just to