Display a notification when content is blocked/insecure

[Jean-Baptiste Lallement]

mako #188

When the content is blocked because it is insecure, nothing happens. Instead the user should be notified and maybe prompted to decide if he wants or not to continue.

This is a major problem for youtube for example because the default scheme when you type youtube in google is https and the content is blocked with this error:
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Detectable autorepeat not supported.
qml: Overriden UA for https://m.youtube.com/?hl=fr&gl=FR : Mozilla/5.0 (Linux; Ubuntu 14.04 like Android 4.4;) AppleWebKit/537.36 Chromium/35.0.1870.2 Mobile Safari/537.36
[0814/165628:WARNING:raw_channel_posix.cc(214)] recvmsg: Connection reset by peer
qml: [JS] (https://m.youtube.com/?hl=fr&gl=FR:9) The key "target-densitydpi" is not supported.
qml: Overriden UA for https://m.youtube.com/feed?ajax=1&layout=mobile&tsp=1&utcoffset=120 : Mozilla/5.0 (Linux; Ubuntu 14.04 like Android 4.4;) AppleWebKit/537.36 Chromium/35.0.1870.2 Mobile Safari/537.36
qml: Overriden UA for https://m.youtube.com/_get_ads?ajax=1&dc_ref=https%3A%2F%2Fm.youtube.com%2F&keyword=mobi.ythome%2Fdefault&layout=mobile&tsp=1&utcoffset=120 : Mozilla/5.0 (Linux; Ubuntu 14.04 like Android 4.4;) AppleWebKit/537.36 Chromium/35.0.1870.2 Mobile Safari/537.36
qml: Overriden UA for https://m.youtube.com/_get_ads?ajax=1&dc_ref=https%3A%2F%2Fm.youtube.com%2F&keyword=mobi.ythome%2Fdefault&layout=mobile&tsp=1&utcoffset=120 : Mozilla/5.0 (Linux; Ubuntu 14.04 like Android 4.4;) AppleWebKit/537.36 Chromium/35.0.1870.2 Mobile Safari/537.36
qml: Overriden UA for https://m.youtube.com/guide_ajax?ajax=1&layout=mobile&tsp=1&utcoffset=120 : Mozilla/5.0 (Linux; Ubuntu 14.04 like Android 4.4;) AppleWebKit/537.36 Chromium/35.0.1870.2 Mobile Safari/537.36
qml: Overriden UA for https://m.youtube.com/watch?ajax=1&ctp=CJsDEKQwIhMIoZ2Y44GTwAIVp83CCh0aYgB7MgpnLWhpZ2gtcmVj&layout=mobile&sts=16294&tsp=1&utcoffset=120&v=MUPjteIxLZE : Mozilla/5.0 (Linux; Ubuntu 14.04 like Android 4.4;) AppleWebKit/537.36 Chromium/35.0.1870.2 Mobile Safari/537.36
qml: [JS] (https://m.youtube.com/watch?v=MUPjteIxLZE:0) [blocked] The page at 'https://m.youtube.com/watch?v=MUPjteIxLZE' was loaded over HTTPS, but displayed insecure content from 'http://r1---sn-aigllnsy.googlevideo.com/videoplayback?sver=3&expire=1408049805&dur=2428.760&fexp=902408%2C927622%2C931983%2C934024%2C934030%2C935660%2C936931%2C938000%2C938631%2C940670%2C946023&source=youtube&ms=au&gir=yes&mv=m&mm=31&clen=45666812&mt=1408028037&key=yt5&lmt=1407989367110544&upn=EsSEQk1fGWE&id=3143e3b5e2312d91&initcwndbps=695000&itag=18&ipbits=0&mws=yes&mime=video%2Fmp4&sparams=clen%2Cdur%2Cgir%2Cid%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Clmt%2Cmime%2Csource%2Cupn%2Cexpire&signature=5F40A797F786CA38CAD819A6F9637DD67BB23646.D25E33ECA570E965DE23CBD76376C4F8ABCDF3F0&nh=IgpwcjAzLmxocjE0Kg03Mi4xNC4yMTMuMjI1&ip=82.246.172.32&cpn=DfICgUnypqXOGVwf': this content should also be loaded over HTTPS.
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TEST CASE:
1. Launch the browser
2. Go to google.com
3. Type youtube
4. The 1rst link on the page should be 'https://m.youtube.com/'
5. Follow this link to youtube and try to play a video

ACTUAL RESULT
It doesn't play because it contains http and https contents.