Restore SnapshotTabHelper temporarily

chrome/renderer/chrome_render_view_observer.h

Index: chrome/renderer/chrome_render_view_observer.h
diff --git a/chrome/renderer/chrome_render_view_observer.h b/chrome/renderer/chrome_render_view_observer.h
index d5297c8ffaadf6a00ec47d52acac769cd7345a08..80247ff53f51bf8afbd4e3daec5cf0f44d136b7f 100644
--- a/chrome/renderer/chrome_render_view_observer.h
+++ b/chrome/renderer/chrome_render_view_observer.h
@@ -126,6 +126,7 @@ class ChromeRenderViewObserver : public content::RenderViewObserver,
                          const string16& jscript,
                          int id,
                          bool notify_result);
+  void OnCaptureSnapshot();
   void OnHandleMessageFromExternalHost(const std::string& message,
                                        const std::string& origin,
                                        const std::string& target);
@@ -149,6 +150,10 @@ class ChromeRenderViewObserver : public content::RenderViewObserver,
   // maximum amount kMaxIndexChars will be placed into the given buffer.
   void CaptureText(WebKit::WebFrame* frame, string16* contents);
 
+  // Capture a snapshot of a view.  This is used to allow an extension
+  // to get a snapshot of a tab using chrome.tabs.captureVisibleTab().
+  bool CaptureSnapshot(WebKit::WebView* view, SkBitmap* snapshot);
+
   ExternalHostBindings* GetExternalHostBindings();
 
   // Determines if a host is in the strict security host set.