Moved the freezing of paint on load of a new url from provisionalLoadStarted to commi...

Moved the freezing of paint on load of a new url from provisionalLoadStarted to committedLoad

[Title]    [Alexa100-5Category]: Combo box is unable to display selected value
[Issue#]   WEB-3772, WEB-3732
[Problem]  On selection change of a drop-down box a new page was being loaded. But the changed value was
           not getting updated in the drop-down box
[Cause]    The painting is suspended for current page in WebFrameLoaderClient::provisionalLoadStarted
           i.e. when the page load starts for new page.
[Solution] Moved suspending of paint from provisional load start to WebFrameLoaderClient::committedLoad. So
           the paint for current page will now be suspended only when the first data for next page is received.
[Cherry-picker] Eunmi Lee - cherry pick this patch to fix N_SE-50906.

Change-Id: If30bc1117128841585b195a121c63874d174d613