Remove unneeded extension_messages_browsertest.cc + cleanup.

chrome/renderer/extensions/chrome_v8_context_set.cc

Index: chrome/renderer/extensions/chrome_v8_context_set.cc
diff --git a/chrome/renderer/extensions/chrome_v8_context_set.cc b/chrome/renderer/extensions/chrome_v8_context_set.cc
index e8ba257627f5a9f41131d286faae393289621543..01cfef126bd341590055438ead063c1d007bd296 100644
--- a/chrome/renderer/extensions/chrome_v8_context_set.cc
+++ b/chrome/renderer/extensions/chrome_v8_context_set.cc
@@ -117,8 +117,10 @@ void ChromeV8ContextSet::DispatchChromeHiddenMethod(
     if ((*it)->v8_context().IsEmpty())
       continue;
 
-    if (!extension_id.empty() && extension_id != (*it)->extension_id())
-      continue;
+    if (!extension_id.empty()) {
+      if (!(*it)->extension() || (extension_id != (*it)->extension()->id()))
+        continue;
+    }
 
     content::RenderView* context_render_view = (*it)->GetRenderView();
     if (!context_render_view)