Support GrabWindowSnapshot with no g_browser_process

chrome/browser/ui/window_snapshot/window_snapshot.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_WINDOW_SNAPSHOT_WINDOW_SNAPSHOT_H_
 #define CHROME_BROWSER_UI_WINDOW_SNAPSHOT_WINDOW_SNAPSHOT_H_
 
 #include <vector>
 
 #include "ui/gfx/native_widget_types.h"
 
 class PrefService;
 
 namespace gfx {
 class Rect;
 }
 
 namespace chrome {
 
 // Grabs a snapshot of the rectangle area |snapshot_bounds| with respect to the
 // top left corner of the designated window and stores a PNG representation
 // into a byte vector. On Windows, |window| may be NULL to grab a snapshot of
-// the primary monitor. Returns true if the operation is successful.
+// the primary monitor. This checks policy settings if taking screenshots is
+// allowed, and is intended to by used by browser code. If you need to take a
+// screenshot for debugging purposes, use ui::GrabWindowSnapshot
+// (ui/window_snapshot/window_snapshot.h).
+// Returns true if the operation is successful (ie. permitted).
 bool GrabWindowSnapshot(
     gfx::NativeWindow window,
     std::vector<unsigned char>* png_representation,
     const gfx::Rect& snapshot_bounds);
 
 void RegisterScreenshotPrefs(PrefService* service);
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_UI_WINDOW_SNAPSHOT_WINDOW_SNAPSHOT_H_