12 RFR(XS) 8214329: SwingMark SubMenus 9% regression in 12-b19 on Linux client

[dean.long at oracle.com]

https://bugs.openjdk.java.net/browse/JDK-8214329
http://cr.openjdk.java.net/~dlong/8214329/webrev/

In "8212605: Pure-Java implementation of AccessController.doPrivileged", 
the stackwalk in JVM_GetStackAccessControlContext was changed from using 
a vframeStream to using a javaVFrame, so that it could access locals. 
However this caused a regression because javaVFrame has more overhead.   
JDK-8215205 fixes the problem by allowing the use of javaVFrame only 
when needed.

This change reverts JVM_GetStackAccessControlContext back to using 
vframeStream, and uses the new API in JDK-8215205 to get a javaVFrame 
lazily.  It also removes two unnecessary calls to java_sender().

dl