[Aura] Added Support for rendering software compositor frames as cc::TextureLayers.

gpu/command_buffer/common/mailbox.cc

Index: gpu/command_buffer/common/mailbox.cc
diff --git a/gpu/command_buffer/common/mailbox.cc b/gpu/command_buffer/common/mailbox.cc
index 653d1d6649599e0bfb4d7a4aa04a0a127062ade8..be2bebf9653ba3a745661ef5775d1c9b19082c82 100644
--- a/gpu/command_buffer/common/mailbox.cc
+++ b/gpu/command_buffer/common/mailbox.cc
@@ -22,6 +22,10 @@ bool Mailbox::IsZero() const {
   return true;
 }
 
+void Mailbox::SetZero() {
+  memset(name, 0, sizeof(name));
+}
+
 void Mailbox::SetName(const int8* n) {
   GPU_DCHECK(IsZero() || !memcmp(name, n, sizeof(name)));
   memcpy(name, n, sizeof(name));