Android: Stop redirecting chrome://welcome to chrome-native://newtab

This is addressing an old TODO, that should be safe to address.

Bug: 455427
Change-Id: I6cdcd6072ef942a49c0e3eb996e2f93df7b293e1
Reviewed-on: https://chromium-review.googlesource.com/c/1496453Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636833}

chrome/browser/android/ntp/new_tab_page_url_handler.cc

@@ -15,7 +15,6 @@
 
 namespace {
 const char kBookmarkFolderPath[] = "folder/";
-const char kLegacyWelcomeHost[] = "welcome";
 }
 
 namespace chrome {
@@ -24,10 +23,7 @@ namespace android {
 bool HandleAndroidNativePageURL(GURL* url,
                                 content::BrowserContext* browser_context) {
   if (url->SchemeIs(content::kChromeUIScheme)) {
-    // TODO(newt): stop redirecting chrome://welcome to chrome-native://newtab
-    // when M39 is a distant memory. http://crbug.com/455427
-    if (url->host() == chrome::kChromeUINewTabHost ||
-        url->host() == kLegacyWelcomeHost) {
+    if (url->host() == chrome::kChromeUINewTabHost) {
       *url = GURL(chrome::kChromeUINativeNewTabURL);
       return true;
     }