Pass result of blockage across content API when new tab blocked.

chrome/browser/background/background_contents_service.cc

Index: chrome/browser/background/background_contents_service.cc
===================================================================
--- chrome/browser/background/background_contents_service.cc	(revision 153532)
+++ chrome/browser/background/background_contents_service.cc	(working copy)
@@ -608,7 +608,7 @@
   return EmptyString16();
 }
 
-void BackgroundContentsService::AddWebContents(
+bool BackgroundContentsService::AddWebContents(
     WebContents* new_contents,
     WindowOpenDisposition disposition,
     const gfx::Rect& initial_pos,
@@ -616,7 +616,8 @@
   Browser* browser = browser::FindLastActiveWithProfile(
       Profile::FromBrowserContext(new_contents->GetBrowserContext()));
   if (browser) {
-    chrome::AddWebContents(browser, NULL, new_contents, disposition,
-                           initial_pos, user_gesture);
+    return chrome::AddWebContents(
+        browser, NULL, new_contents, disposition, initial_pos, user_gesture);
   }
+  return true;
 }