The sidebar icon remains in a disabled state in the Network tab even after selecting a resource. The second selection of a resource activates the sidebar icon. Additionally, after reloading, clicking the sidebar icon before selecting a resource does nothing. Then when you select a resource, the sidebar opens with the resource. If the sidebar icon is disabled, it shouldn't toggle anything to open. However, I think it should always be clickable and if no resource selection exists, the main document should auto-select and open the sidebar.
<rdar://problem/21709833>
I wonder if there is an exception that is causing this. Can you inspect the inspector to check? http://trac.webkit.org/wiki/WebInspectorDebugging
Created attachment 256321 [details] Shows disabled sidebar icon, and reluctance of sidebar to open. I could not get the second behavior to repro in this video. Clicking the sidebar icon with no resource selected, then selecting the resource does not open the sidebar as it did when I was first noticing the behavior.
Created attachment 256406 [details] Patch
Comment on attachment 256406 [details] Patch r=me
Comment on attachment 256406 [details] Patch Clearing flags on attachment: 256406 Committed r186540: <http://trac.webkit.org/changeset/186540>
All reviewed patches have been landed. Closing bug.