Add an 'allow-top-navigation-with-user-interaction' sandbox flag.

third_party/WebKit/Source/core/dom/SandboxFlags.cpp

Index: third_party/WebKit/Source/core/dom/SandboxFlags.cpp
diff --git a/third_party/WebKit/Source/core/dom/SandboxFlags.cpp b/third_party/WebKit/Source/core/dom/SandboxFlags.cpp
index c4b7c8b893075946853aa0ce0dd1e7f571d2af4a..4b92e6656517dfb8465fd2dc4dd1456e9e249dd5 100644
--- a/third_party/WebKit/Source/core/dom/SandboxFlags.cpp
+++ b/third_party/WebKit/Source/core/dom/SandboxFlags.cpp
@@ -27,6 +27,7 @@
 #include "core/dom/SandboxFlags.h"
 
 #include "core/html/parser/HTMLParserIdioms.h"
+#include "platform/RuntimeEnabledFeatures.h"
 #include "wtf/text/StringBuilder.h"
 
 namespace blink {
@@ -65,6 +66,11 @@ SandboxFlags parseSandboxPolicy(const SpaceSplitString& policy,
       flags &= ~SandboxModals;
     } else if (equalIgnoringCase(sandboxToken, "allow-presentation")) {
       flags &= ~SandboxPresentation;
+    } else if (equalIgnoringCase(sandboxToken,
+                                 "allow-top-navigation-with-user-activation") &&
+               RuntimeEnabledFeatures::
+                   topNavWithUserActivationInSandboxEnabled()) {
+      flags &= ~SandboxTopNavigationWithUserActivation;
     } else {
       if (numberOfTokenErrors)
         tokenErrors.append(", '");