Fixing two Qt bustages. First, calling MakeFullScreen on child windows is bad as they are displayed. Second, the Qt version we are using has bugs with window activation and we added a XSync before calling showFullScreen to avoid such cases. r=oleg

widget/src/qt/nsWindow.cpp

@@ -64,6 +64,8 @@
 #include <QPinchGesture>
 #endif // QT version check
 
+#include "nsXULAppAPI.h"
+
 #include "prlink.h"
 
 #include "nsWindow.h"
@@ -1848,7 +1850,11 @@ nsWindow::NativeShow(PRBool aAction)
 {
     if (aAction) {
         QWidget *widget = GetViewWidget();
-        if (widget && !widget->isVisible())
+        // On e10s, we never want the child process or plugin process
+        // to go fullscreen because if we do the window because visible
+        // do to disabled Qt-Xembed
+        if ((XRE_GetProcessType() == GeckoProcessType_Default) &&
+            widget && !widget->isVisible())
             MakeFullScreen(mSizeMode == nsSizeMode_Fullscreen);
         mWidget->show();
     }
@@ -1925,6 +1931,12 @@ nsWindow::MakeFullScreen(PRBool aFullScreen)
             mLastSizeMode = mSizeMode;
 
         mSizeMode = nsSizeMode_Fullscreen;
+#ifdef Q_WS_X11
+        // Some versions of Qt (4.6.x) crash in XSetInputFocus due to
+        // unsynchronized window activation.  Sync here to avoid such
+        // cases.
+        XSync(QX11Info().display(), False);
+#endif
         widget->showFullScreen();
     }
     else {