We can no longer assume that there is only one process during layout tests

Now that we reuse devtools processes during layout tests, it can happen
that there are multiple processes during session history tests.

Remove the now spurious NOTREACHED()

BUG=474162
R=mkwst@chromium.org

Review URL: https://codereview.chromium.org/1069293002

Cr-Commit-Position: refs/heads/master@{#324199}

content/shell/browser/webkit_test_controller.cc

@@ -631,11 +631,9 @@ void WebKitTestController::OnCaptureSessionHistory() {
     WebContents* web_contents = (*window)->web_contents();
     // Only capture the history from windows in the same process as the main
     // window. During layout tests, we only use two processes when an
-    // devtools window is open. This should not happen during history navigation
-    // tests.
+    // devtools window is open.
     if (render_view_host->GetProcess() !=
         web_contents->GetRenderViewHost()->GetProcess()) {
-      NOTREACHED();
       continue;
     }
     routing_ids.push_back(web_contents->GetRenderViewHost()->GetRoutingID());