PlzNavigate: add cancel navigation logic for uncommitted requests

content/browser/frame_host/navigation_before_commit_info.h

Index: content/browser/frame_host/navigation_before_commit_info.h
diff --git a/content/browser/frame_host/navigation_before_commit_info.h b/content/browser/frame_host/navigation_before_commit_info.h
index 506723df92ab779520cdad9719e7b95459de83ac..68a047a6c1346c4c7024b5be7a66f43ecb88fe48 100644
--- a/content/browser/frame_host/navigation_before_commit_info.h
+++ b/content/browser/frame_host/navigation_before_commit_info.h
@@ -8,6 +8,8 @@
 #include <string>
 
 #include "base/basictypes.h"
+#include "base/time/time.h"
+#include "content/common/content_export.h"
 #include "content/public/common/page_transition_types.h"
 #include "content/public/common/referrer.h"
 #include "url/gurl.h"
@@ -20,7 +22,7 @@ namespace content {
 // thread where it should be used to send a FrameMsg_CommitNavigation message to
 // the renderer.
 struct NavigationBeforeCommitInfo {
-  NavigationBeforeCommitInfo() {};
+  CONTENT_EXPORT NavigationBeforeCommitInfo();
 
   // The url that is actually being loaded.
   GURL navigation_url;
@@ -35,6 +37,9 @@ struct NavigationBeforeCommitInfo {
   // The navigationStart time to expose to JS for this navigation.
   // TODO(clamy): Add the other values that matter to the Navigation Timing API.
   base::TimeTicks browser_navigation_start;
+
+  // The unique ID of this navigation request.
+  int64 navigation_request_id;
 };
 
 }  // namespace content