navigation: Retain a screenshot of the page before it unloads

content/browser/web_contents/navigation_entry_impl.cc

Index: content/browser/web_contents/navigation_entry_impl.cc
diff --git a/content/browser/web_contents/navigation_entry_impl.cc b/content/browser/web_contents/navigation_entry_impl.cc
index 53d70aaf7cbbfd868cdd20bbd1fa0b21ff0eba63..d647b8fb16b80dc12e491c1c90e04825f5bdcf15 100644
--- a/content/browser/web_contents/navigation_entry_impl.cc
+++ b/content/browser/web_contents/navigation_entry_impl.cc
@@ -271,4 +271,9 @@ bool NavigationEntryImpl::GetCanLoadLocalResources() const {
   return can_load_local_resources_;
 }
 
+void NavigationEntryImpl::SetScreenshotPNGData(
+    const std::vector<unsigned char>& png_data) {
+  screenshot_ = new base::RefCountedBytes(png_data);
+}
+
 }  // namespace content