Bug 427511 - Some UI is painted outside of its area with GTK 3.10

Use default cairo object for painting Tree.

- Use the cairo object passed in by GTK to do the painting
  instead of creating a new one.
- Prevent resetting of clipping.
- Remove code specific to GTK > 3.9

Change-Id: I902b04fc2410f05c1c927fd261dcaa31d04b3cbb
Signed-off-by: Sami Wagiaalla <swagiaal@redhat.com>
Bug 449546 - [responsiveness] No error logged when UI froze during
opening type hierarchy on java.lang.Object on Mac

Fix uses of display#sendPreEvent and display#sendPostEvent in
Synchronizer.java

Change-Id: I152868ec432396ce0c453c8976727444f7a74a8f
Signed-off-by: Arun Thondapu <arunkumar.thondapu@in.ibm.com>