Revert 177827 "WebGL: Free temporary GPU resources held by inact..."

trunk/Source/core/html/HTMLCanvasElement.cpp

Index: trunk/Source/core/html/HTMLCanvasElement.cpp
===================================================================
--- trunk/Source/core/html/HTMLCanvasElement.cpp	(revision 177853)
+++ trunk/Source/core/html/HTMLCanvasElement.cpp	(working copy)
@@ -650,15 +650,17 @@
 
 void HTMLCanvasElement::didChangeVisibilityState(PageVisibilityState visibility)
 {
-    if (!m_context)
-        return;
-    bool hidden = visibility != PageVisibilityStateVisible;
-    m_context->setIsHidden(hidden);
-    if (hidden) {
-        clearCopiedImage();
-        if (is3D()) {
-            discardImageBuffer();
+    if (hasImageBuffer()) {
+        bool hidden = visibility != PageVisibilityStateVisible;
+        if (hidden) {
+            clearCopiedImage();
+            if (is3D()) {
+                discardImageBuffer();
+            }
         }
+        if (hasImageBuffer()) {
+            m_imageBuffer->setIsHidden(hidden);
+        }
     }
 }