Do not return std::unique_ptr<T>() in various dirs.

This is just a convoluted way of writing nullptr, so rewrite it in the
simpler form. PRESUBMIT.py already disallows new instances of
std::unique_ptr<T>(). This removes existing instances.

Change-Id: Iee6f46b016c61a5308f701cfec2d067fe9390a32
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2803679
Reviewed-by: Andrey Kosyakov <[email protected]>
Reviewed-by: Xiyuan Xia <[email protected]>
Reviewed-by: Sami Kyöstilä <[email protected]>
Reviewed-by: Sean Topping <[email protected]>
Reviewed-by: Alex Gough <[email protected]>
Reviewed-by: Steven Bennetts <[email protected]>
Reviewed-by: Victor Costan <[email protected]>
Reviewed-by: Sylvain Defresne <[email protected]>
Reviewed-by: Lambros Lambrou <[email protected]>
Reviewed-by: Guido Urdaneta <[email protected]>
Commit-Queue: Lei Zhang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#870130}
diff --git a/remoting/host/touch_injector_win.cc b/remoting/host/touch_injector_win.cc
index ac434cd..d1f4894 100644
--- a/remoting/host/touch_injector_win.cc
+++ b/remoting/host/touch_injector_win.cc
@@ -114,7 +114,7 @@
   base::ScopedNativeLibrary library(base::FilePath(L"User32.dll"));
   if (!library.is_valid()) {
     PLOG(INFO) << "Failed to get library module for touch injection functions.";
-    return std::unique_ptr<TouchInjectorWinDelegate>();
+    return nullptr;
   }
 
   InitializeTouchInjectionFunction init_func =
@@ -122,7 +122,7 @@
           library.GetFunctionPointer("InitializeTouchInjection"));
   if (!init_func) {
     PLOG(INFO) << "Failed to get InitializeTouchInjection function handle.";
-    return std::unique_ptr<TouchInjectorWinDelegate>();
+    return nullptr;
   }
 
   InjectTouchInputFunction inject_touch_func =
@@ -130,7 +130,7 @@
           library.GetFunctionPointer("InjectTouchInput"));
   if (!inject_touch_func) {
     PLOG(INFO) << "Failed to get InjectTouchInput.";
-    return std::unique_ptr<TouchInjectorWinDelegate>();
+    return nullptr;
   }
 
   return std::unique_ptr<TouchInjectorWinDelegate>(new TouchInjectorWinDelegate(