As pointed out in a previous patch review, some native Canvas methods do not
receive a native canvas handle and instead have to use GraphicsJNI to query
the object mNativeCanvasWrapper field.
To avoid the extra JNI call, this change adds the missing Java wrapper
methods and ensures that all native calls are passed efficient native
handles.
Also, some native methods are consolidated: save, saveAll -> save,
clipRect* -> clipRect.
Change-Id: I2eae4a633f6a463d9fbae2ca632661acc8b5cfc3
95d49149cc