Revert of cc: Remove use of PassAs() and constructor-casting with scoped_ptr.

cc/test/test_web_graphics_context_3d.cc

Index: cc/test/test_web_graphics_context_3d.cc
diff --git a/cc/test/test_web_graphics_context_3d.cc b/cc/test/test_web_graphics_context_3d.cc
index 7f839f2aa0fc1f4289458f0f86efa46ba28789b3..e1e0f409f3bf13fb5b03915e7e8e404e14c3db72 100644
--- a/cc/test/test_web_graphics_context_3d.cc
+++ b/cc/test/test_web_graphics_context_3d.cc
@@ -502,7 +502,7 @@
   DCHECK_EQ(target, buffers.get(bound_buffer_)->target);
   Buffer* buffer = buffers.get(bound_buffer_);
   if (context_lost_) {
-    buffer->pixels = nullptr;
+    buffer->pixels.reset();
     return;
   }
 
@@ -541,7 +541,7 @@
   base::ScopedPtrHashMap<unsigned, Buffer>& buffers = namespace_->buffers;
   DCHECK_GT(buffers.count(bound_buffer_), 0u);
   DCHECK_EQ(target, buffers.get(bound_buffer_)->target);
-  buffers.get(bound_buffer_)->pixels = nullptr;
+  buffers.get(bound_buffer_)->pixels.reset();
   return true;
 }