Add new permission string for extensions that override new tab pages.

chrome/common/extensions/chrome_manifest_url_handlers.cc

Index: chrome/common/extensions/chrome_manifest_url_handlers.cc
diff --git a/chrome/common/extensions/chrome_manifest_url_handlers.cc b/chrome/common/extensions/chrome_manifest_url_handlers.cc
index cb6a0e9ec4858eded4e6eef20d342745f053640b..59238d89b794816a1eb4155b0f4bdf16b32bdf1b 100644
--- a/chrome/common/extensions/chrome_manifest_url_handlers.cc
+++ b/chrome/common/extensions/chrome_manifest_url_handlers.cc
@@ -142,8 +142,16 @@ bool URLOverridesHandler::Parse(Extension* extension, base::string16* error) {
     *error = base::ASCIIToUTF16(errors::kMultipleOverrides);
     return false;
   }
+
+  // If this is an NTP override extension, add the NTP override permission.
+  if (url_overrides->chrome_url_overrides_.count(chrome::kChromeUINewTabHost)) {
+    PermissionsParser::AddAPIPermission(extension,
+                                        APIPermission::kNewTabPageOverride);
+  }
+
   extension->SetManifestData(keys::kChromeURLOverrides,
                              std::move(url_overrides));
+
   return true;
 }