Enable building WebView bundles by default

These are now being build on the official builders, so it probably makes
sense to enable by default.

Bug: 1033098
Change-Id: I04224c174ac3de526cadd26f05fe34fdd77d2ac1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2145821
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#758873}

android_webview/system_webview_apk_tmpl.gni

@@ -19,7 +19,7 @@ declare_args() {
   system_webview_package_name = "com.android.webview"
 
   # Whether to enable standalone and trichrome WebView bundle build targets.
-  enable_webview_bundles = false
+  enable_webview_bundles = true
 }
 
 template("system_webview_apk_or_module_tmpl") {