aura: Ensure OwnedMailbox not used with invalid or destroyed GLHelper.

content/browser/aura/owned_mailbox.cc

Index: content/browser/aura/owned_mailbox.cc
diff --git a/content/browser/aura/owned_mailbox.cc b/content/browser/aura/owned_mailbox.cc
index 1a99d335ac245f3760d29c29af9c7ae531eb632b..5994903b33220a908dba061a304f1830e535f6c1 100644
--- a/content/browser/aura/owned_mailbox.cc
+++ b/content/browser/aura/owned_mailbox.cc
@@ -18,11 +18,8 @@ OwnedMailbox::OwnedMailbox(GLHelper* gl_helper)
 }
 
 OwnedMailbox::~OwnedMailbox() {
-  ImageTransportFactory::GetInstance()->RemoveObserver(this);
-  if (gl_helper_) {
-    gl_helper_->WaitSyncPoint(sync_point_);
-    gl_helper_->DeleteTexture(texture_id_);
-  }
+  if (gl_helper_)
+    Destroy();
 }
 
 void OwnedMailbox::UpdateSyncPoint(uint32 sync_point) {
@@ -30,7 +27,8 @@ void OwnedMailbox::UpdateSyncPoint(uint32 sync_point) {
     sync_point_ = sync_point;
 }
 
-void OwnedMailbox::OnLostResources() {
+void OwnedMailbox::Destroy() {
+  ImageTransportFactory::GetInstance()->RemoveObserver(this);
   gl_helper_->WaitSyncPoint(sync_point_);
   gl_helper_->DeleteTexture(texture_id_);
   texture_id_ = 0;
@@ -39,4 +37,9 @@ void OwnedMailbox::OnLostResources() {
   gl_helper_ = NULL;
 }
 
+void OwnedMailbox::OnLostResources() {
+  if (gl_helper_)
+    Destroy();
+}
+
 }  // namespace content