Use gpu::Mailbox in IPCs instead of std::string

gpu/command_buffer/service/mailbox_manager.cc

Index: gpu/command_buffer/service/mailbox_manager.cc
diff --git a/gpu/command_buffer/service/mailbox_manager.cc b/gpu/command_buffer/service/mailbox_manager.cc
index 90193934f3a4dd40ba797266978847b653241e69..ccc48eb957ff185f080115ca804419a3f857b007 100644
--- a/gpu/command_buffer/service/mailbox_manager.cc
+++ b/gpu/command_buffer/service/mailbox_manager.cc
@@ -8,6 +8,7 @@
 
 #include "base/rand_util.h"
 #include "crypto/hmac.h"
+#include "gpu/command_buffer/common/mailbox.h"
 #include "gpu/command_buffer/service/gl_utils.h"
 #include "gpu/command_buffer/service/texture_definition.h"
 
@@ -19,6 +20,10 @@ MailboxName::MailboxName() {
   std::fill(signature, signature + sizeof(signature), 0);
 }
 
+MailboxName::MailboxName(const ::gpu::Mailbox& mailbox) {
+  std::copy(mailbox.name, mailbox.name + sizeof(mailbox.name), key);
+}
+
 MailboxManager::MailboxManager()
     : hmac_(crypto::HMAC::SHA256),
       textures_(std::ptr_fun(&MailboxManager::TargetNameLess)) {