This fixes an InvalidRead error that valgrind found.

TEST=ran valgrind on chromeos version of chrome.
BUG=none
Review URL: http://codereview.chromium.org/1807006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@45867 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/tab_contents/thumbnail_generator.cc

@@ -393,7 +393,10 @@ void ThumbnailGenerator::TabContentsDisconnected(TabContents* contents) {
   RenderWidgetHost* renderer = contents->render_view_host();
   while (iterator != callback_map_.end()) {
     if (iterator->second->renderer == renderer) {
-      callback_map_.erase(iterator);
+      ThumbnailCallbackMap::iterator nuked = iterator;
+      ++iterator;
+      callback_map_.erase(nuked);
+      continue;
     }
     ++iterator;
   }