[wip] Introduce SiteInstanceKeepAlive.

content/browser/frame_host/navigation_entry_screenshot_manager.h

Index: content/browser/frame_host/navigation_entry_screenshot_manager.h
diff --git a/content/browser/frame_host/navigation_entry_screenshot_manager.h b/content/browser/frame_host/navigation_entry_screenshot_manager.h
index 072d6fd4a7fe19a1111acdb6b2e5c6c470f92285..1c6cdf38717ecd486d8a8a10c85d7ae81ac28c93 100644
--- a/content/browser/frame_host/navigation_entry_screenshot_manager.h
+++ b/content/browser/frame_host/navigation_entry_screenshot_manager.h
@@ -6,6 +6,7 @@
 #define CONTENT_BROWSER_FRAME_HOST_NAVIGATION_ENTRY_SCREENSHOT_MANAGER_H_
 
 #include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
 #include "content/common/content_export.h"
@@ -18,6 +19,7 @@ class NavigationControllerImpl;
 class NavigationEntryImpl;
 class RenderViewHost;
 class ScreenshotData;
+class SiteInstanceKeepAlive;
 
 // NavigationEntryScreenshotManager takes care of taking image-captures for the
 // current navigation entry of a NavigationControllerImpl, and managing these
@@ -50,6 +52,7 @@ class CONTENT_EXPORT NavigationEntryScreenshotManager {
   // The callback invoked when taking the screenshot of the page is complete.
   // This sets the screenshot on the navigation entry.
   void OnScreenshotTaken(int unique_id,
+                         scoped_ptr<SiteInstanceKeepAlive> site_instance,
                          bool success,
                          const SkBitmap& bitmap);