Enable cropping window capturing for Win7 when Aero is disabled.

webrtc/modules/desktop_capture/win/window_capture_utils.cc

 /*
  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 25 matching lines @@
         rect.left + border.width(),
         rect.top,
         rect.right - border.width(),
         rect.bottom - border.height());
   } else {
     *cropped_rect = *original_rect;
   }
   return true;
 }
 
+AeroChecker::AeroChecker() : dwmapi_library_(nullptr), func_(nullptr) {
+  // Try to load dwmapi.dll dynamically since it is not available on XP.
+  dwmapi_library_ = LoadLibrary(L"dwmapi.dll");
+  if (dwmapi_library_) {
+    func_ = reinterpret_cast<DwmIsCompositionEnabledFunc>(
+        GetProcAddress(dwmapi_library_, "DwmIsCompositionEnabled"));
+  }
+}
+
+AeroChecker::~AeroChecker() {
+  if (dwmapi_library_) {
+    FreeLibrary(dwmapi_library_);
+  }
+}
+
+bool AeroChecker::IsAeroEnabled() {
+  BOOL result = FALSE;
+  if (func_) {
+    func_(&result);
+  }
+  return result != FALSE;
+}
+
 }  // namespace webrtc