content_shell: avoid debug crashing for mid-clicks on links.

content/shell/browser/shell.cc

Index: content/shell/browser/shell.cc
diff --git a/content/shell/browser/shell.cc b/content/shell/browser/shell.cc
index c8616d31a1eac3a6469f1079895fb24c97861693..df096555b4264ede583d6568a0e65fd7ef7007ab 100644
--- a/content/shell/browser/shell.cc
+++ b/content/shell/browser/shell.cc
@@ -230,8 +230,9 @@ gfx::NativeView Shell::GetContentView() {
 
 WebContents* Shell::OpenURLFromTab(WebContents* source,
                                    const OpenURLParams& params) {
-  // The only one we implement for now.
-  DCHECK(params.disposition == CURRENT_TAB);
+  // CURRENT_TAB is the only one we implement for now.
+  if (params.disposition != CURRENT_TAB)
+      return NULL;
   NavigationController::LoadURLParams load_url_params(params.url);
   load_url_params.referrer = params.referrer;
   load_url_params.transition_type = params.transition;