Replace NULL with nullptr in all C++ files.

webrtc/modules/desktop_capture/desktop_region_unittest.cc

Index: webrtc/modules/desktop_capture/desktop_region_unittest.cc
diff --git a/webrtc/modules/desktop_capture/desktop_region_unittest.cc b/webrtc/modules/desktop_capture/desktop_region_unittest.cc
index 16f86260964bc6af2604c2d7286f5b460f94ca24..c84aeef009004d92a02f0f7fbfa6bd67cee8bcde 100644
--- a/webrtc/modules/desktop_capture/desktop_region_unittest.cc
+++ b/webrtc/modules/desktop_capture/desktop_region_unittest.cc
@@ -43,7 +43,7 @@ void CompareRegion(const DesktopRegion& region,
 // Verify that regions are empty when created.
 TEST(DesktopRegionTest, Empty) {
   DesktopRegion r;
-  CompareRegion(r, NULL, 0);
+  CompareRegion(r, nullptr, 0);
 }
 
 // Verify that empty rectangles are ignored.
@@ -51,7 +51,7 @@ TEST(DesktopRegionTest, AddEmpty) {
   DesktopRegion r;
   DesktopRect rect = DesktopRect::MakeXYWH(1, 2, 0, 0);
   r.AddRect(rect);
-  CompareRegion(r, NULL, 0);
+  CompareRegion(r, nullptr, 0);
 }
 
 // Verify that regions with a single rectangles are handled properly.