The sun.java2d.loops.BlitBg.Generic loop doesn't do proper
clipping of the source and destination surfaces.

Run the attached test case, and it will fail with the following:
Testing source: BufferedImage@186768e: type = 2 DirectColorModel: rmask=ff0000 gmask=ff00 bmask=ff amask=ff000000 IntegerInterleavedRaster: width = 50 height = 50 #Bands = 4 xOff = 0 yOff = 0 dataOffset[0] 0
testing blit rect src: java.awt.Rectangle[x=0,y=0,width=30,height=30]
                  dst: java.awt.Rectangle[x=-10,y=-10,width=30,height=30]
calculated dest rect:java.awt.Rectangle[x=0,y=0,width=20,height=20]
subtest passed
testing blit rect src: java.awt.Rectangle[x=-10,y=-10,width=50,height=50]
                  dst: java.awt.Rectangle[x=0,y=0,width=50,height=50]
calculated dest rect:java.awt.Rectangle[x=10,y=10,width=40,height=40]
Test failed at x=0 y=0
 expected: ff00ff00 got:ffff0000
Exception in thread "AWT-EventQueue-0" java.lang.RuntimeException: Test failed at x=0 y=0
        at SourceClippingBlitTest.test(SourceClippingBlitTest.java:212)
        at SourceClippingBlitTest.runTests(SourceClippingBlitTest.java:133)
        at SourceClippingBlitTest$1.windowActivated(SourceClippingBlitTest.java:69)

It fails with the default, d3d and opengl pipelines starting at least
on 1.5 (haven't tested earlier releases) through 1.7 (b18).