[ios] Snapshot for WebState

ios/web/public/web_state/web_state.h

Index: ios/web/public/web_state/web_state.h
diff --git a/ios/web/public/web_state/web_state.h b/ios/web/public/web_state/web_state.h
index 6974f523942f2691752762d1a997bb86f4d2338b..8335bb8545ff37d38ce5963c23aab69f0801057a 100644
--- a/ios/web/public/web_state/web_state.h
+++ b/ios/web/public/web_state/web_state.h
@@ -35,6 +35,10 @@ class DictionaryValue;
 class Value;
 }
 
+namespace gfx {
+class Image;
+}
+
 namespace web {
 
 class BrowserState;
@@ -248,6 +252,14 @@ class WebState : public base::SupportsUserData {
   // CreateParams::created_with_opener for more details.
   virtual bool HasOpener() const = 0;
 
+  // Callback used to handle snapshots. The parameter is the snapshot image.
+  typedef base::Callback<void(const gfx::Image&)> SnapshotCallback;
+
+  // Takes a snapshot of this WebState with |target_size|. |callback| is
+  // asynchronously invoked after performing the snapshot.
+  virtual void TakeSnapshot(const SnapshotCallback& callback,
+                            CGSize target_size) const = 0;
+
  protected:
   friend class WebStateObserver;
   friend class WebStatePolicyDecider;