Bug 604395 - OpenGL contexts use uninitialized format, often resulting in failure to create - r+sr=vladimir, a=bjacob:trust me, we want this in beta7.

Note: pushed by bjacob -- so complain to me if you're not happy about that.

gfx/thebes/GLContext.h

@@ -295,10 +295,11 @@ struct THEBES_API ContextFormat
     };
 
     ContextFormat() {
-        memset(this, 0, sizeof(this));
+        memset(this, 0, sizeof(*this));
     }
 
     ContextFormat(const StandardContextFormat cf) {
+        memset(this, 0, sizeof(*this));
         switch (cf) {
         case BasicRGBA32:
             red = green = blue = alpha = 8;