Convert //printing to use std::unique_ptr

printing/printing_context_win_unittest.cc

Index: printing/printing_context_win_unittest.cc
diff --git a/printing/printing_context_win_unittest.cc b/printing/printing_context_win_unittest.cc
index b71442b0ee198ea00ae67e5240ce9633e6fefbc2..fc6fee0ced3d791175a89f528d85f47770aab0d8 100644
--- a/printing/printing_context_win_unittest.cc
+++ b/printing/printing_context_win_unittest.cc
@@ -162,7 +162,7 @@ TEST_F(PrintingContextTest, Base) {
   PrintSettings settings;
   settings.set_device_name(GetDefaultPrinter());
   // Initialize it.
-  scoped_ptr<PrintingContext> context(PrintingContext::Create(this));
+  std::unique_ptr<PrintingContext> context(PrintingContext::Create(this));
   EXPECT_EQ(PrintingContext::OK, context->InitWithSettings(settings));
 
   // The print may lie to use and may not support world transformation.