Changing check in didChangePageScaleFactor and pageDidRequestScroll

This makes more sense, and let we perform a restoring change even if the
new scale factor or content position is equal to the current one

Reviewed by: Hugo Parente Lima
Changing m_duringPageTransition flag to m_duringFrameRendering

didCommitLoad for frame can be called several times for the same
page, so make much more sense to put this flag name related to
frame rendering

Reviewed by: Hugo Parente Lima
Setting m_contentScaleFactor when there is no pending scale in WebViewNix

Also removing unecessary flag check in didRenderFrame

Reviewed by: Hugo Parente Lima
MiniBrowser: Adjusting scale after WebView has rendered frame if is an standard load type

Reviewed by: Hugo Parente Lima