application development - Extend existing QML Component from C++ plugin

First of all, I would like to say that I'm not very experienced in Qt, but I would like to include a new feature in existing QML WebView component to set a list of header values, included User Agent header, to be sent when requesting a new url. The way to perform it I thought to be subclassing QWebView class (for example 'MyWebView' extending QWebView) and register that class with

qmlRegisterType(uri, 1, 0, "MyWebView");

I have created a "QML Extension Library + Tabbed Touch UI" application called MyApp to register MyWebView class, when coded, using precreated backend class. The only thing I have done until now is creating a first approach .h file this way:

#ifndef MYWEBVIEW_H
#define MYWEBVIEW_H
#include 
class MyWebView : public QWebView
{
    Q_OBJECT
public:
    explicit MyWebView(QWebView *parent = 0);
};
#endif // MYWEBVIEW_H

with this .cpp

#include "mywebview.h"
MyWebView::MyWebView(QWebView *parent) :
    QWebView(parent)
{
}

I don't have any device connected to my laptop, so I only use Raring Ringtail desktop distribution for developing. With this extra added file, compilation works, but when I try to run or debug the project (to see at least the default MyApp.qml working) these errors are shown:

Starting /usr/lib/x86_64-linux-gnu/qt5/bin/qmlscene...

file:///[DEBUG_PATH]/app/MyApp.qml:30 Type HelloTab unavailable
file:///[DEBUG_PATH]/app/ui/HelloTab.qml:3 plugin cannot be loaded for
module "MyApp": Cannot load library
[DEBUG_PATH]/backend/modules/MyApp/libMyApp.so:
([DEBUG_PATH]/backend/modules/MyApp/libMyApp.so: undefined symbol:
_ZN8QWebView16staticMetaObjectE)

so I suppose... is something not well configured? Does you have any idea of what is happenning?

Could it be possible the Ubuntu version I am using is 64bit?. Whey I execute

ldd -r libMyApp.so

there are may lines saying WebKit classes are undefined:

    linux-vdso.so.1 =>  (0x00007ffffb5d1000)
    libQt5Qml.so.5 => /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5 (0x00007ff9e1baa000)
    libQt5Core.so.5 => /usr/lib/x86_64-linux-gnu/libQt5Core.so.5 (0x00007ff9e1595000)
    libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007ff9e1291000)
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007ff9e107b000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007ff9e0cb3000)
    libQt5Network.so.5 => /usr/lib/x86_64-linux-gnu/libQt5Network.so.5 (0x00007ff9e097b000)
    libQt5V8.so.5 => /usr/lib/x86_64-linux-gnu/libQt5V8.so.5 (0x00007ff9e0337000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007ff9e0032000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007ff9dfe14000)
    libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007ff9dfbfd000)
    libicui18n.so.48 => /usr/lib/x86_64-linux-gnu/libicui18n.so.48 (0x00007ff9df837000)
    libicuuc.so.48 => /usr/lib/x86_64-linux-gnu/libicuuc.so.48 (0x00007ff9df4cb000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007ff9df2c7000)
    libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007ff9defcb000)
    librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007ff9dedc2000)
    /lib64/ld-linux-x86-64.so.2 (0x00007ff9e2205000)
    libicudata.so.48 => /usr/lib/x86_64-linux-gnu/libicudata.so.48 (0x00007ff9dda52000)
    libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007ff9dd812000)
undefined symbol: _ZN8QWebView16staticMetaObjectE   (./libMyApp.so)
undefined symbol: _ZN8QWebView5eventEP6QEvent   (./libMyApp.so)
undefined symbol: _ZNK7QWidget7devTypeEv    (./libMyApp.so)
undefined symbol: _ZN7QWidget10setVisibleEb (./libMyApp.so)
undefined symbol: _ZNK8QWebView8sizeHintEv  (./libMyApp.so)
undefined symbol: _ZNK7QWidget15minimumSizeHintEv   (./libMyApp.so)
undefined symbol: _ZNK7QWidget14heightForWidthEi    (./libMyApp.so)
undefined symbol: _ZNK7QWidget17hasHeightForWidthEv (./libMyApp.so)
undefined symbol: _ZNK7QWidget11paintEngineEv   (./libMyApp.so)
undefined symbol: _ZN8QWebView15mousePressEventEP11QMouseEvent  (./libMyApp.so)
undefined symbol: _ZN8QWebView17mouseReleaseEventEP11QMouseEvent    (./libMyApp.so)
undefined symbol: _ZN8QWebView21mouseDoubleClickEventEP11QMouseEvent    (./libMyApp.so)
undefined symbol: _ZN8QWebView14mouseMoveEventEP11QMouseEvent   (./libMyApp.so)
undefined symbol: _ZN8QWebView10wheelEventEP11QWheelEvent   (./libMyApp.so)
undefined symbol: _ZN8QWebView13keyPressEventEP9QKeyEvent   (./libMyApp.so)
undefined symbol: _ZN8QWebView15keyReleaseEventEP9QKeyEvent (./libMyApp.so)
undefined symbol: _ZN8QWebView12focusInEventEP11QFocusEvent (./libMyApp.so)
undefined symbol: _ZN8QWebView13focusOutEventEP11QFocusEvent    (./libMyApp.so)
undefined symbol: _ZN7QWidget10enterEventEP6QEvent  (./libMyApp.so)
undefined symbol: _ZN7QWidget10leaveEventEP6QEvent  (./libMyApp.so)
undefined symbol: _ZN8QWebView10paintEventEP11QPaintEvent   (./libMyApp.so)
undefined symbol: _ZN7QWidget9moveEventEP10QMoveEvent   (./libMyApp.so)
undefined symbol: _ZN8QWebView11resizeEventEP12QResizeEvent (./libMyApp.so)
undefined symbol: _ZN7QWidget10closeEventEP11QCloseEvent    (./libMyApp.so)
undefined symbol: _ZN8QWebView16contextMenuEventEP17QContextMenuEvent   (./libMyApp.so)
undefined symbol: _ZN7QWidget11tabletEventEP12QTabletEvent  (./libMyApp.so)
undefined symbol: _ZN7QWidget11actionEventEP12QActionEvent  (./libMyApp.so)
undefined symbol: _ZN8QWebView14dragEnterEventEP15QDragEnterEvent   (./libMyApp.so)
undefined symbol: _ZN8QWebView13dragMoveEventEP14QDragMoveEvent (./libMyApp.so)
undefined symbol: _ZN8QWebView14dragLeaveEventEP15QDragLeaveEvent   (./libMyApp.so)
undefined symbol: _ZN8QWebView9dropEventEP10QDropEvent  (./libMyApp.so)
undefined symbol: _ZN7QWidget9showEventEP10QShowEvent   (./libMyApp.so)
undefined symbol: _ZN7QWidget9hideEventEP10QHideEvent   (./libMyApp.so)
undefined symbol: _ZN7QWidget11nativeEventERK10QByteArrayPvPl   (./libMyApp.so)
undefined symbol: _ZN8QWebView11changeEventEP6QEvent    (./libMyApp.so)
undefined symbol: _ZNK7QWidget6metricEN12QPaintDevice17PaintDeviceMetricE   (./libMyApp.so)
undefined symbol: _ZNK7QWidget11initPainterEP8QPainter  (./libMyApp.so)
undefined symbol: _ZNK7QWidget10redirectedEP6QPoint (./libMyApp.so)
undefined symbol: _ZNK7QWidget13sharedPainterEv (./libMyApp.so)
undefined symbol: _ZN8QWebView16inputMethodEventEP17QInputMethodEvent   (./libMyApp.so)
undefined symbol: _ZNK8QWebView16inputMethodQueryEN2Qt16InputMethodQueryE   (./libMyApp.so)
undefined symbol: _ZN8QWebView18focusNextPrevChildEb    (./libMyApp.so)
undefined symbol: _ZN8QWebView12createWindowEN8QWebPage13WebWindowTypeE (./libMyApp.so)
undefined symbol: _ZThn16_NK7QWidget7devTypeEv  (./libMyApp.so)
undefined symbol: _ZThn16_NK7QWidget11paintEngineEv (./libMyApp.so)
undefined symbol: _ZThn16_NK7QWidget6metricEN12QPaintDevice17PaintDeviceMetricE (./libMyApp.so)
undefined symbol: _ZThn16_NK7QWidget11initPainterEP8QPainter    (./libMyApp.so)
undefined symbol: _ZThn16_NK7QWidget10redirectedEP6QPoint   (./libMyApp.so)
undefined symbol: _ZThn16_NK7QWidget13sharedPainterEv   (./libMyApp.so)
undefined symbol: _ZTI8QWebView (./libMyApp.so)
undefined symbol: _ZN8QWebPage16staticMetaObjectE   (./libMyApp.so)
undefined symbol: _ZN8QWebPage5eventEP6QEvent   (./libMyApp.so)
undefined symbol: _ZN8QWebPage13triggerActionENS_9WebActionEb   (./libMyApp.so)
undefined symbol: _ZN8QWebPage9extensionENS_9ExtensionEPKNS_15ExtensionOptionEPNS_15ExtensionReturnE    (./libMyApp.so)
undefined symbol: _ZNK8QWebPage17supportsExtensionENS_9ExtensionE   (./libMyApp.so)
undefined symbol: _ZN8QWebPage25shouldInterruptJavaScriptEv (./libMyApp.so)
undefined symbol: _ZN8QWebPage12createWindowENS_13WebWindowTypeE    (./libMyApp.so)
undefined symbol: _ZN8QWebPage12createPluginERK7QStringRK4QUrlRK11QStringListS8_    (./libMyApp.so)
undefined symbol: _ZN8QWebPage23acceptNavigationRequestEP9QWebFrameRK15QNetworkRequestNS_14NavigationTypeE  (./libMyApp.so)
undefined symbol: _ZN8QWebPage10chooseFileEP9QWebFrameRK7QString    (./libMyApp.so)
undefined symbol: _ZN8QWebPage15javaScriptAlertEP9QWebFrameRK7QString   (./libMyApp.so)
undefined symbol: _ZN8QWebPage17javaScriptConfirmEP9QWebFrameRK7QString (./libMyApp.so)
undefined symbol: _ZN8QWebPage16javaScriptPromptEP9QWebFrameRK7QStringS4_PS2_   (./libMyApp.so)
undefined symbol: _ZN8QWebPage24javaScriptConsoleMessageERK7QStringiS2_ (./libMyApp.so)
undefined symbol: _ZNK8QWebPage15userAgentForUrlERK4QUrl    (./libMyApp.so)
undefined symbol: _ZTI8QWebPage (./libMyApp.so)
undefined symbol: _ZN8QWebView11qt_metacastEPKc (./libMyApp.so)
undefined symbol: _ZN8QWebViewD2Ev  (./libMyApp.so)
undefined symbol: _ZN8QWebView11qt_metacallEN11QMetaObject4CallEiPPv    (./libMyApp.so)
undefined symbol: _ZN8QWebPage11qt_metacallEN11QMetaObject4CallEiPPv    (./libMyApp.so)
undefined symbol: _ZN8QWebViewC2EP7QWidget  (./libMyApp.so)
undefined symbol: _ZN8QWebPageD2Ev  (./libMyApp.so)
undefined symbol: _ZN8QWebPage11qt_metacastEPKc (./libMyApp.so)
undefined symbol: _ZN8QWebPageC2EP7QObject  (./libMyApp.so)