fix NSDrawer live resizing
fix NSDrawer live resizing

Stick to the current _contentSize instead of looking at the actual content,
so the drawer doesn't change size uncommandedly.

crystax/android-vendor-cocotron,JackLian/cocotron,yuhangwang/cocotron,gemu2015/cocotron-sierra,Suninus/cocotron,ruppmatt/cocotron,gemu2015/cocotron-sierra,cjwl/cocotron,yuhangwang/cocotron,Suninus/cocotron,crystax/android-vendor-cocotron,ruppmatt/cocotron,JackLian/cocotron,guestOS/guestOS,crystax/android-vendor-cocotron,gemu2015/cocotron-sierra,JackLian/cocotron,yuhangwang/cocotron,cjwl/cocotron,cneira/cocotron,cyclaero/cocotron,cyclaero/cocotron,yuhangwang/cocotron,guestOS/guestOS,cjwl/cocotron,Suninus/cocotron,cneira/cocotron,cjwl/cocotron,cyclaero/cocotron,ruppmatt/cocotron,crystax/android-vendor-cocotron,cneira/cocotron,guestOS/guestOS,guestOS/guestOS,Suninus/cocotron,cneira/cocotron,gemu2015/cocotron-sierra,JackLian/cocotron,ruppmatt/cocotron,cyclaero/cocotron