[AW] DevUI: Button to open the correct DevUI in error dialog

Add the button to change WebView provider as a neutral dialog button
instead of overriding the existing positive button to open the correct
WebView DevUI. This error dialog is shown when the dev ui is launched
from a package that is different from the selected as the system's
webview provider.

Fixed: 1041606
Test: Manually change WebView provider and go back to wrong dev ui, inspect the dialog to see the two buttons
Change-Id: I21e8f5f4b2d3b9d9c608df0abbe299442e2e9453
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2036068Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Commit-Queue: Hazem Ashmawy <hazems@chromium.org>
Auto-Submit: Hazem Ashmawy <hazems@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738533}

android_webview/nonembedded/java/src/org/chromium/android_webview/devui/WebViewPackageError.java

@@ -130,7 +130,7 @@ public class WebViewPackageError {
 
         // Switching WebView providers is possible from API >= 24.
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
-            builder.setPositiveButton("Change WebView provider",
+            builder.setNeutralButton("Change WebView provider",
                     (dialog, id)
                             -> mContext.startActivity(
                                     new Intent(Settings.ACTION_WEBVIEW_SETTINGS)));