Add a setting to allow window object reuse across a top-level initial navigation.

third_party/WebKit/Source/core/frame/Settings.in

Index: third_party/WebKit/Source/core/frame/Settings.in
diff --git a/third_party/WebKit/Source/core/frame/Settings.in b/third_party/WebKit/Source/core/frame/Settings.in
index 47d06413661eb4fbe19981900c90caffa9da86bd..7e027832a8283dbc861296706cd37d34b9c30337 100644
--- a/third_party/WebKit/Source/core/frame/Settings.in
+++ b/third_party/WebKit/Source/core/frame/Settings.in
@@ -214,6 +214,12 @@ useWideViewport initial=true, invalidate=ViewportDescription
 # http://developer.android.com/reference/android/webkit/WebSettings.html#setLoadWithOverviewMode(boolean)
 loadWithOverviewMode initial=true, invalidate=ViewportDescription
 
+# Used by android_webview to support legacy apps that inject script into a top-level initial empty
+# document and expect it to persist on navigation, even though the origin is unique. Note that this
+# behavior violates the requirements described by [Initialising a new Document object] in
+# https://html.spec.whatwg.org/multipage/browsers.html#navigating-across-documents.
+shouldReuseGlobalForUnownedMainFrame initial=false
+
 ######## End of settings used by Android WebView ########