From aba970f2a872b445515cd261cc8eca288676a49e Mon Sep 17 00:00:00 2001
From: Morris Tseng <mtseng@mozilla.com>
Date: Fri, 16 Oct 2015 10:01:53 +0800
Subject: [PATCH] Bug 1214571 - Only create mContextObserver once. r=baku

--HG--
extra : commitid : JlT1u9F257B
extra : rebase_source : 7898e6c864c6851e05f47425462d5048483c9633
---
 dom/html/HTMLCanvasElement.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/dom/html/HTMLCanvasElement.cpp b/dom/html/HTMLCanvasElement.cpp
index 1d2c8dae1821..fcaa822906f1 100644
--- a/dom/html/HTMLCanvasElement.cpp
+++ b/dom/html/HTMLCanvasElement.cpp
@@ -400,7 +400,9 @@ HTMLCanvasElement::CreateContext(CanvasContextType aContextType)
   // Add Observer for webgl canvas.
   if (aContextType == CanvasContextType::WebGL1 ||
       aContextType == CanvasContextType::WebGL2) {
-    mContextObserver = new HTMLCanvasElementObserver(this);
+    if (!mContextObserver) {
+      mContextObserver = new HTMLCanvasElementObserver(this);
+    }
   }
 
   ret->SetCanvasElement(this);
@@ -779,7 +781,9 @@ HTMLCanvasElement::TransferControlToOffscreen(ErrorResult& aRv)
                                            sz.height,
                                            GetCompositorBackendType(),
                                            renderer);
-    mContextObserver = new HTMLCanvasElementObserver(this);
+    if (!mContextObserver) {
+      mContextObserver = new HTMLCanvasElementObserver(this);
+    }
   } else {
     aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
   }