navigation: Retain a screenshot of the page before it unloads

content/browser/web_contents/navigation_controller_impl.h

Index: content/browser/web_contents/navigation_controller_impl.h
diff --git a/content/browser/web_contents/navigation_controller_impl.h b/content/browser/web_contents/navigation_controller_impl.h
index 5fd8b14899befcd4d8bdf27bcd2567ecae5d0244..3443ff1770fb2d14abe4cac99c9e2da92feef728 100644
--- a/content/browser/web_contents/navigation_controller_impl.h
+++ b/content/browser/web_contents/navigation_controller_impl.h
@@ -17,6 +17,10 @@
 
 struct ViewHostMsg_FrameNavigate_Params;
 
+namespace skia {
+class PlatformBitmap;
+}
+
 namespace content {
 class NavigationEntryImpl;
 class WebContentsImpl;
@@ -308,6 +312,15 @@ class CONTENT_EXPORT NavigationControllerImpl
   // specified |offset|.  The index returned is not guaranteed to be valid.
   int GetIndexForOffset(int offset) const;
 
+  // Takes a screenshot of the page at the current state.
+  void TakeScreenshot();
+
+  // The callback invoked when taking the screenshot of the page is complete.
+  // This sets the screenshot on the navigation entry.
+  void TakingScreenshotComplete(NavigationEntryImpl* entry,
+                                skia::PlatformBitmap* bitmap,
+                                bool success);
+
   // ---------------------------------------------------------------------------
 
   // The user browser context associated with this controller.