[wip] Introduce SiteInstanceKeepAlive.

content/browser/frame_host/navigation_entry_screenshot_manager.cc

Index: content/browser/frame_host/navigation_entry_screenshot_manager.cc
diff --git a/content/browser/frame_host/navigation_entry_screenshot_manager.cc b/content/browser/frame_host/navigation_entry_screenshot_manager.cc
index b2bf429dc0a6c66a34266a5267ed62267a8aacb6..466241a3ee1c6ea94c2f85a0eb94245b937884fe 100644
--- a/content/browser/frame_host/navigation_entry_screenshot_manager.cc
+++ b/content/browser/frame_host/navigation_entry_screenshot_manager.cc
@@ -11,6 +11,7 @@
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/browser/render_widget_host_view.h"
+#include "content/public/browser/site_instance.h"
 #include "content/public/common/content_switches.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkPaint.h"
@@ -134,11 +135,16 @@ void NavigationEntryScreenshotManager::TakeScreenshotImpl(
     NavigationEntryImpl* entry) {
   DCHECK(host && host->GetView());
   DCHECK(entry);
+  scoped_refptr<SiteInstanceImpl> site_instance(
+      static_cast<SiteInstanceImpl*>(host->GetSiteInstance()));
+  scoped_ptr<SiteInstanceKeepAlive> keep_alive(

[mfomitchev, 2014/02/14 16:21:36]

Why not just keep_alive = site_instance->AcquireKeepAlive()? AcquireKeepAlive()
already returns a scoped_ptr..

+      site_instance->AcquireKeepAlive());
   host->CopyFromBackingStore(gfx::Rect(),
       host->GetView()->GetViewBounds().size(),
       base::Bind(&NavigationEntryScreenshotManager::OnScreenshotTaken,
                  screenshot_factory_.GetWeakPtr(),
-                 entry->GetUniqueID()));
+                 entry->GetUniqueID(),
+                 base::Passed(&keep_alive)));
 }
 
 void NavigationEntryScreenshotManager::SetMinScreenshotIntervalMS(
@@ -147,9 +153,12 @@ void NavigationEntryScreenshotManager::SetMinScreenshotIntervalMS(
   min_screenshot_interval_ms_ = interval_ms;
 }
 
-void NavigationEntryScreenshotManager::OnScreenshotTaken(int unique_id,
-                                                     bool success,
-                                                     const SkBitmap& bitmap) {
+void NavigationEntryScreenshotManager::OnScreenshotTaken(
+    int unique_id,
+    scoped_ptr<SiteInstanceKeepAlive> site_instance,

[mfomitchev, 2014/02/14 16:21:36]

rename this to keep_alive?

+    bool success,
+    const SkBitmap& bitmap) {
+  site_instance.reset();

[mfomitchev, 2014/02/14 16:21:36]

The biggest question for me is whether this will guarantee that everything will
eventually get destroyed properly. I played around with this fix a bit, and RWH
and RFH don't seem to get destroyed after the navigation completes, at least not
right away.

   NavigationEntryImpl* entry = NULL;
   int entry_count = owner_->GetEntryCount();
   for (int i = 0; i < entry_count; ++i) {