[devtools] Support different encodings for Page.CaptureScreenshot.

ui/snapshot/snapshot_ios.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/snapshot/snapshot.h"
 
 #include "base/callback.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/image/image.h"
 
 namespace ui {
 
 bool GrabViewSnapshot(gfx::NativeView view,
-                      std::vector<unsigned char>* png_representation,
+                      gfx::Image* image,
                       const gfx::Rect& snapshot_bounds) {
   // TODO(bajones): Implement iOS snapshot functionality
   return false;
 }
 
 bool GrabWindowSnapshot(gfx::NativeWindow window,
-                        std::vector<unsigned char>* png_representation,
+                        gfx::Image* image,
                         const gfx::Rect& snapshot_bounds) {
   // TODO(bajones): Implement iOS snapshot functionality
   return false;
 }
 
 void GrabWindowSnapshotAndScaleAsync(
     gfx::NativeWindow window,
     const gfx::Rect& snapshot_bounds,
     const gfx::Size& target_size,
     scoped_refptr<base::TaskRunner> background_task_runner,
     GrabWindowSnapshotAsyncCallback callback) {
   callback.Run(gfx::Image());
 }
 
-void GrabViewSnapshotAsync(
-    gfx::NativeView view,
-    const gfx::Rect& source_rect,
-    scoped_refptr<base::TaskRunner> background_task_runner,
-    const GrabWindowSnapshotAsyncPNGCallback& callback) {
-  callback.Run(scoped_refptr<base::RefCountedBytes>());
+void GrabViewSnapshotAsync(gfx::NativeView view,
+                           const gfx::Rect& source_rect,
+                           const GrabWindowSnapshotAsyncCallback& callback) {
+  callback.Run(gfx::Image());
 }
 
-void GrabWindowSnapshotAsync(
-    gfx::NativeWindow window,
-    const gfx::Rect& source_rect,
-    scoped_refptr<base::TaskRunner> background_task_runner,
-    const GrabWindowSnapshotAsyncPNGCallback& callback) {
-  callback.Run(scoped_refptr<base::RefCountedBytes>());
+void GrabWindowSnapshotAsync(gfx::NativeWindow window,
+                             const gfx::Rect& source_rect,
+                             const GrabWindowSnapshotAsyncCallback& callback) {
+  callback.Run(gfx::Image());
 }
 
 }  // namespace ui