hkmwsesuv
sailfish-browser-1.17.7-1.12.5.jolla.armv7hl.rpm

https://github.com/sailfishos/sailfish-browser/commit/66e744da14fc4268bfd232678386496016aa3a57#diff-ba3c890c29799181dff248914805b990

declarativewebcontainer.cpp
void DeclarativeWebContainer::updateContentOrientation(Qt::ScreenOrientation orientation)
{
    if (gForceLandscapeToPortrait) {

	if (orientation == Qt::PortraitOrientation) {
            orientation = Qt::InvertedLandscapeOrientation;
        }

	else if (orientation == Qt::InvertedPortraitOrientation) {
            orientation = Qt::LandscapeOrientation;
        }

        else if (orientation == Qt::LandscapeOrientation) {
            orientation = Qt::PortraitOrientation;
        }

	else if (orientation == Qt::InvertedLandscapeOrientation) {
            orientation = Qt::InvertedPortraitOrientation;
        }
    }

    if (m_mozWindow) {
        bool orientationShouldChange = (orientation != m_mozWindow->pendingOrientation());
        m_mozWindow->setContentOrientation(orientation);
        if (orientationShouldChange) {
            emit pendingWebContentOrientationChanged();
        }
    }

    if (gForceLandscapeToPortrait) {

	if (orientation == Qt::InvertedLandscapeOrientation) {
            orientation = Qt::PortraitOrientation;
        }

	else if (orientation == Qt::LandscapeOrientation) {
            orientation = Qt::InvertedPortraitOrientation;
        }

        else if (orientation == Qt::PortraitOrientation) {
            orientation = Qt::LandscapeOrientation;
        }

	else if (orientation == Qt::InvertedPortraitOrientation) {
            orientation = Qt::InvertedLandscapeOrientation;
        }
    }
    reportContentOrientationChange(orientation);
}

browserpage.qml
    function inputMaskForOrientation(orientation) {
        // mask is in portrait window coordinates
        var mask = Qt.rect(0, 0, Screen.width, Screen.height)
        if (!window.opaqueBackground && webView.enabled && browserPage.active && !webView.touchBlocked && !downloadPopup.visible) {
            var overlayVisibleHeight = browserPage.height - overlay.y

            switch (orientation) {
            case Orientation.None:
            case Orientation.Landscape:
                mask.y = overlay.y
                // fallthrough
            case Orientation.LandscapeInverted:
                mask.height = overlayVisibleHeight
                break

            case Orientation.PortraitInverted:
                mask.x = overlay.y
                // fallthrough
            case Orientation.Portrait:
                mask.width = overlayVisibleHeight
            }
        }
        return mask
    }

sailfish-browser.spec
Version:    1.17.7
Release:    1.12.5.jolla

70-browser.conf
BROWSER_FORCE_LANDSCAPE_TO_PORTRAIT="1"