[Extensions] Don't allow content scripts on the New Tab Page

extensions/common/manifest_constants.cc

Index: extensions/common/manifest_constants.cc
diff --git a/extensions/common/manifest_constants.cc b/extensions/common/manifest_constants.cc
index d34920c4144cff1570ea7eede71e71e22b62eacc..9e6e250e9b4ae18858fa238d616d0f6199077d08 100644
--- a/extensions/common/manifest_constants.cc
+++ b/extensions/common/manifest_constants.cc
@@ -291,6 +291,7 @@ const char kCannotClaimAllURLsInExtent[] =
     "Cannot claim all URLs in an extent.";
 const char kCannotScriptGallery[] =
     "The extensions gallery cannot be scripted.";
+const char kCannotScriptNtp[] = "The New Tab Page cannot be scripted.";
 const char kCannotScriptSigninPage[] =
     "The sign-in page cannot be scripted.";
 const char kChromeVersionTooLow[] =