Bug 896138 patch 1:  Move RestyleTracker and OverflowChangedTracker out of nested namespace mozilla::css (which shouldn't exist) into namespace mozilla.  r=heycam
Bug 896138 patch 2:  Add a RestyleManager class.  r=heycam

The later patches in this series will move restyling code into this file
from nsCSSFrameConstructor and nsFrameManager.
Bug 896138 patch 3:  Remove forward declaration of struct that hasn't been in this class since changeset e0df6dfdaaca (Bug 479655 part 3).  r=heycam
Bug 896138 patch 4:  Move restyle management code from nsCSSFrameConstructor to RestyleManager.  r=heycam

This moves restyling management out of nsCSSFrameConstructor (thus
reducing its size), and keeps the restyling code closer together.

This is the first of two big chunks of code moved in this patch series.
A later patch in this series will move related code from nsFrameManager
into the same destination file.
Bug 896138 patch 5:  Expose UndisplayedNode list from nsFrameManager.  r=heycam

This is needed for the following patch, which leaves the undisplayed map
in nsFrameManager rather than moving it to RestyleManager (I think one
could argue for either way, but it was easier not to move it).
Bug 896138 patch 6:  Move restyle management code from nsFrameManager to RestyleManager.  r=heycam

This is the second of two big chunks of code moved into the new
RestyleManager class from another sources.

Note that the undisplayed map remains in nsFrameManager, although it
could perhaps have moved.
Bug 896138 patch 7:  Remove unused aFrameManager parameters to some functions.  r=heycam
Bug 896138 patch 8:  Add setter for RestyleManager::mInStyleRefresh rather than using friend.  r=heycam (within review comments for patch 4)

(The friend declaration is still needed for access to RestyleElement,
which I'd rather leave private.)
Bug 896138 patch 9:  Move RecomputePosition to a more logical place in the .cpp file, near other hint handling implementations.  No review.