Fix setting the top-level FrameTreeNode name for named windows.

BUG=486889

Review URL: https://codereview.chromium.org/1141453003

Cr-Commit-Position: refs/heads/master@{#329543}
diff --git a/content/public/browser/web_contents.h b/content/public/browser/web_contents.h
index a28df1c..62f09a8 100644
--- a/content/public/browser/web_contents.h
+++ b/content/public/browser/web_contents.h
@@ -110,6 +110,11 @@
     int routing_id;
     int main_frame_routing_id;
 
+    // The name of the top-level frame of the new window. It is non-empty
+    // when creating a named window (e.g. <a target="foo"> or
+    // window.open('', 'bar')).
+    std::string main_frame_name;
+
     // Initial size of the new WebContent's view. Can be (0, 0) if not needed.
     gfx::Size initial_size;