Fixed the broken <spark-splitter>
Fixed the broken <spark-splitter>

Some recent change in Polymer has changed the way custom elements get registered. As a result of that, and possibly some wrong Polymer usage in Spark, all Xyz.created ctors for Spark widgets were called twice. Calling real initialization from there for SparkSplitter caused a crash on the second call, because _target would be initialized to null for some reason. Redone to use enteredView(), which is probably more correct anyway.

2947721120/chromedeveditor,2947721120/choredev,b0dh1sattva/chromedeveditor,vivalaralstin/chromedeveditor,devoncarew/spark,modulexcite/chromedeveditor,devoncarew/spark,googlearchive/chromedeveditor,2947721120/choredev,yikaraman/chromedeveditor,ussuri/chromedeveditor,yikaraman/chromedeveditor,beaufortfrancois/chromedeveditor,yikaraman/chromedeveditor,yikaraman/chromedeveditor,2947721120/choredev,hxddh/chromedeveditor,googlearchive/chromedeveditor,hxddh/chromedeveditor,beaufortfrancois/chromedeveditor,2947721120/choredev,beaufortfrancois/chromedeveditor,b0dh1sattva/chromedeveditor,vivalaralstin/chromedeveditor,modulexcite/chromedeveditor,2947721120/choredev,googlearchive/chromedeveditor,beaufortfrancois/chromedeveditor,ussuri/chromedeveditor,2947721120/chromedeveditor,valmzetvn/chromedeveditor,ussuri/chromedeveditor,beaufortfrancois/chromedeveditor,2947721120/chromedeveditor,2947721120/chromedeveditor,devoncarew/spark,valmzetvn/chromedeveditor,devoncarew/spark,vivalaralstin/chromedeveditor,valmzetvn/chromedeveditor,b0dh1sattva/chromedeveditor,googlearchive/chromedeveditor,b0dh1sattva/chromedeveditor,vivalaralstin/chromedeveditor,valmzetvn/chromedeveditor,ussuri/chromedeveditor,b0dh1sattva/chromedeveditor,b0dh1sattva/chromedeveditor,ussuri/chromedeveditor,2947721120/chromedeveditor,vivalaralstin/chromedeveditor,b0dh1sattva/chromedeveditor,yikaraman/chromedeveditor,googlearchive/chromedeveditor,beaufortfrancois/chromedeveditor,valmzetvn/chromedeveditor,vivalaralstin/chromedeveditor,modulexcite/chromedeveditor,2947721120/chromedeveditor,2947721120/choredev,hxddh/chromedeveditor,ussuri/chromedeveditor,devoncarew/spark,modulexcite/chromedeveditor,ussuri/chromedeveditor,hxddh/chromedeveditor,yikaraman/chromedeveditor,devoncarew/spark,hxddh/chromedeveditor,hxddh/chromedeveditor,valmzetvn/chromedeveditor,yikaraman/chromedeveditor,googlearchive/chromedeveditor,modulexcite/chromedeveditor,2947721120/choredev,valmzetvn/chromedeveditor,vivalaralstin/chromedeveditor,2947721120/chromedeveditor,beaufortfrancois/chromedeveditor,modulexcite/chromedeveditor,modulexcite/chromedeveditor,hxddh/chromedeveditor,googlearchive/chromedeveditor