Add is_srcdoc to FrameNavigationEntry and restore about::srcdoc URL.

content/browser/frame_host/frame_navigation_entry.h

Index: content/browser/frame_host/frame_navigation_entry.h
diff --git a/content/browser/frame_host/frame_navigation_entry.h b/content/browser/frame_host/frame_navigation_entry.h
index eca2712e788460b4eed86682a92671bf4521949e..b27f56d4e3aebedd1e2c8594aa51ed2ca011ad89 100644
--- a/content/browser/frame_host/frame_navigation_entry.h
+++ b/content/browser/frame_host/frame_navigation_entry.h
@@ -39,7 +39,8 @@ class CONTENT_EXPORT FrameNavigationEntry
                        const GURL& url,
                        const Referrer& referrer,
                        const std::string& method,
-                       int64_t post_id);
+                       int64_t post_id,
+                       bool is_srcdoc);
 
   // Creates a copy of this FrameNavigationEntry that can be modified
   // independently from the original.
@@ -56,7 +57,8 @@ class CONTENT_EXPORT FrameNavigationEntry
                    const std::vector<GURL>& redirect_chain,
                    const PageState& page_state,
                    const std::string& method,
-                   int64_t post_id);
+                   int64_t post_id,
+                   bool is_srcdoc);
 
   // The unique name of the frame this entry is for.  This is a stable name for
   // the frame based on its position in the tree and relation to other named
@@ -134,6 +136,9 @@ class CONTENT_EXPORT FrameNavigationEntry
   // is not a POST.
   scoped_refptr<ResourceRequestBodyImpl> GetPostData() const;
 
+  // Whether the navigation is for an iframe with srcdoc attribute.
+  bool is_srcdoc() const { return is_srcdoc_; }
+
  private:
   friend class base::RefCounted<FrameNavigationEntry>;
   virtual ~FrameNavigationEntry();
@@ -162,6 +167,7 @@ class CONTENT_EXPORT FrameNavigationEntry
   PageState page_state_;
   std::string method_;
   int64_t post_id_;
+  bool is_srcdoc_;
 
   DISALLOW_COPY_AND_ASSIGN(FrameNavigationEntry);
 };