<AWT Dev> [9] Review Request: 8138764 In some cases the usage of TreeLock can be replaced by other synchronization

[Sergey Bylokhov]

Hello.
Please review the fix for jdk9, I plan to backport it to jdk8.

In this fix some of synchronizations on TreeLock were removed.

- Component.java(CachedPainter.java) : long time ago this 
synchronization was necessary, because the getGC method iterated over 
hierarchy of components[1], but now it simple getter.
- Window.java : locationByPlatform and opacity are changed to volatile 
and an additional synchronization is removed.

These changes are subset of my fix for JDK-6765536, which is safe to 
backport to jdk8.

[1] 
http://hg.openjdk.java.net/jdk6/jdk6/jdk/diff/e7ecde4010e9/src/share/classes/java/awt/Component.java

Bug: https://bugs.openjdk.java.net/browse/JDK-8138764
Webrev can be found at: http://cr.openjdk.java.net/~serb/8138764/webrev.00

-- 
Best regards, Sergey.