Remove the ability of webpages to specify strings for the onbeforeunload dialog.

components/app_modal_strings.grdp

Index: components/app_modal_strings.grdp
diff --git a/components/app_modal_strings.grdp b/components/app_modal_strings.grdp
index 09cd5ff616289a3ba885c2e67f0384fde031fd7a..0be1e6a2ec901aae72a9d0ba9fbcb103790356e0 100644
--- a/components/app_modal_strings.grdp
+++ b/components/app_modal_strings.grdp
@@ -22,8 +22,8 @@
   <message name="IDS_BEFOREUNLOAD_MESSAGEBOX_TITLE" desc="Title for the 'before unload' dialog.">
     Confirm Navigation
   </message>
-  <message name="IDS_BEFOREUNLOAD_MESSAGEBOX_FOOTER" desc="Text shown at the bottom of the dialog, after the message provided by the script.">
-    Are you sure you want to leave this page?
+  <message name="IDS_BEFOREUNLOAD_MESSAGEBOX_MESSAGE" desc="Text shown as the message of the 'before unload' dialog.">
+    This page is warning you that if you leave this page, data may be lost. Are you sure you want to leave this page?
   </message>
   <message name="IDS_BEFOREUNLOAD_MESSAGEBOX_OK_BUTTON_LABEL" desc="The text on the button which navigates the user away from the page.">
     Leave this Page
@@ -36,8 +36,8 @@
   <message name="IDS_BEFORERELOAD_MESSAGEBOX_TITLE" desc="Title for the 'before reload' dialog.">
     Confirm Reload
   </message>
-  <message name="IDS_BEFORERELOAD_MESSAGEBOX_FOOTER" desc="Text shown at the bottom of the dialog, after the message provided by the script.">
-    Are you sure you want to reload this page?
+  <message name="IDS_BEFORERELOAD_MESSAGEBOX_MESSAGE" desc="Text shown as the message of the 'before reload' dialog.">

[Charlie Reis, 2016/02/18 21:37:13]

nit: 'before unload' dialog for reloads.

(There's no beforereload event, which is what this sounds like.)

[Avi (use Gerrit), 2016/02/18 21:42:26]

Done.

+    This page is warning you that if you reload this page, data may be lost. Are you sure you want to reload this page?
   </message>
   <message name="IDS_BEFORERELOAD_MESSAGEBOX_OK_BUTTON_LABEL" desc="The text on the button which reloads the page.">
     Reload this Page