GPU: 'Pass' SharedMemory when possible.

gpu/command_buffer/common/buffer.cc

Index: gpu/command_buffer/common/buffer.cc
diff --git a/gpu/command_buffer/common/buffer.cc b/gpu/command_buffer/common/buffer.cc
index f0ddbd0c873e732ebb6a55059d80d929e69bd2ea..5ba4e51ec01d0d3b88ea07967a5fe6d86ef48210 100644
--- a/gpu/command_buffer/common/buffer.cc
+++ b/gpu/command_buffer/common/buffer.cc
@@ -4,12 +4,16 @@
 
 #include "gpu/command_buffer/common/buffer.h"
 
+#include "base/logging.h"
+
 namespace gpu {
 
 Buffer::Buffer(scoped_ptr<base::SharedMemory> shared_memory, size_t size)
     : shared_memory_(shared_memory.Pass()),
       memory_(shared_memory_->memory()),
-      size_(size) {}
+      size_(size) {
+  DCHECK(memory_) << "The memory must be mapped to create a Buffer";
+}
 
 Buffer::~Buffer() {}