Bug 677531 - GLXtest process stays around as zombie until the data is used by GfxInfo - r=matt.woodrow

This gave zombies staying around when using layers.acceleration.force-enabled or .disabled or safe-mode, for instance.

widget/src/xpwidgets/nsBaseWidget.cpp

@@ -828,22 +828,30 @@ nsBaseWidget::GetShouldAccelerate()
   if (xr)
     xr->GetInSafeMode(&safeMode);
 
+  bool whitelisted = false;
+
+  // bug 655578: on X11 at least, we must always call GetFeatureStatus (even if we don't need that information)
+  // as that's what causes GfxInfo initialization which kills the zombie 'glxtest' process.
+  nsCOMPtr<nsIGfxInfo> gfxInfo = do_GetService("@mozilla.org/gfx/info;1");
+  if (gfxInfo) {
+    PRInt32 status;
+    if (NS_SUCCEEDED(gfxInfo->GetFeatureStatus(nsIGfxInfo::FEATURE_OPENGL_LAYERS, &status))) {
+      if (status == nsIGfxInfo::FEATURE_NO_INFO) {
+        whitelisted = true;
+      }
+    }
+  }
+
   if (disableAcceleration || safeMode)
     return PR_FALSE;
 
   if (forceAcceleration)
     return PR_TRUE;
   
-  nsCOMPtr<nsIGfxInfo> gfxInfo = do_GetService("@mozilla.org/gfx/info;1");
-  if (gfxInfo) {
-    PRInt32 status;
-    if (NS_SUCCEEDED(gfxInfo->GetFeatureStatus(nsIGfxInfo::FEATURE_OPENGL_LAYERS, &status))) {
-      if (status != nsIGfxInfo::FEATURE_NO_INFO) {
+  if (!whitelisted) {
     NS_WARNING("OpenGL-accelerated layers are not supported on this system.");
     return PR_FALSE;
   }
-    }
-  }
 
   if (accelerateByDefault)
     return PR_TRUE;