Fix imbalanced keepalive count for event pages when dealing with other views.

chrome/browser/extensions/extension_process_manager.h

Index: chrome/browser/extensions/extension_process_manager.h
diff --git a/chrome/browser/extensions/extension_process_manager.h b/chrome/browser/extensions/extension_process_manager.h
index a43e552cb7a039ef602aaff50fedc0c4405cb3a0..adaa7fd1495968fb40f7ea3cfba5d280e728e38d 100644
--- a/chrome/browser/extensions/extension_process_manager.h
+++ b/chrome/browser/extensions/extension_process_manager.h
@@ -194,6 +194,9 @@ class ExtensionProcessManager : public content::NotificationObserver {
   // was not available when the host was first registered.
   void UpdateRegisteredRenderView(content::RenderViewHost* render_view_host);
 
+  // Clears background page data for this extension.
+  void ClearBackgroundPageData(const std::string& extension_id);
+
   BackgroundPageDataMap background_page_data_;
 
   // The time to delay between an extension becoming idle and