Use RgbaColor in DesktopFrameGenerator and add RgbaColorTest

webrtc/modules/desktop_capture/rgba_color_unittest.cc

Index: webrtc/modules/desktop_capture/rgba_color_unittest.cc
diff --git a/webrtc/modules/desktop_capture/rgba_color_unittest.cc b/webrtc/modules/desktop_capture/rgba_color_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..33e4fb7474125f48790ec76814490e14548ec649
--- /dev/null
+++ b/webrtc/modules/desktop_capture/rgba_color_unittest.cc
@@ -0,0 +1,44 @@
+/*
+ *  Copyright (c) 2016 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.
+ */
+
+#include "webrtc/modules/desktop_capture/rgba_color.h"
+
+#include <vector>
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace webrtc {
+
+TEST(RgbaColorTest, ConvertFromAndToUInt32) {
+  static const std::vector<uint32_t> cases{
+      0,         1000,       2693,       3725,       4097,      12532,

[Sergey Ulanov, 2016/09/13 00:47:48]

How was this table generated? are these arbitrary values or is there some logic
here?

[Hzj_jie, 2016/09/13 18:48:10]

Except for several specific numbers, like 0, 1000, 65535, 65536, UINT32_MAX,
others are sorted random numbers in [0, UINT32_MAX).

+      19902,     27002,      27723,      30944,      65535,     65536,
+      231194,    255985,     322871,     883798,     9585200,   12410056,
+      12641940,  30496970,   105735668,  110117847,  482769275, 542368468,
+      798173396, 2678656711, 3231043200, UINT32_MAX,
+  };
+
+  for (uint32_t value : cases) {
+    RgbaColor left(value);
+    ASSERT_EQ(left.ToUInt32(), value);
+    RgbaColor right(left);
+    ASSERT_EQ(left.ToUInt32(), right.ToUInt32());
+  }
+}
+
+TEST(RgbaColorTest, AlphaChannelEquality) {
+  RgbaColor left(10, 10, 10, 0);
+  RgbaColor right(10, 10, 10, 255);
+  ASSERT_EQ(left, right);
+  right.alpha = 128;
+  ASSERT_NE(left, right);
+}
+
+}  // namespace webrtc