Reduce window rectangles cap to 8

src/gpu/gl/GrGLGpu.cpp

Index: src/gpu/gl/GrGLGpu.cpp
diff --git a/src/gpu/gl/GrGLGpu.cpp b/src/gpu/gl/GrGLGpu.cpp
index 3e44138328d884a36bfbad1e1820f3e0d6fa8aa4..cd6c0e6c8314a7ce6c5956846a29a1c448eca582 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -2009,12 +2009,13 @@ void GrGLGpu::flushWindowRectangles(const GrWindowRectangles& windows, const GrG
 
     GrGLIRect glwindows[GrWindowRectangles::kMaxWindows];
     const SkIRect* skwindows = windows.data();
-    for (int i = 0; i < windows.count(); ++i) {
+    int numWindows = SkTMin(windows.count(), int(GrWindowRectangles::kMaxWindows));

[bsalomon, 2016/08/20 16:37:31]

We can't just assert here? Is that the nature of the bug?

[csmartdalton, 2016/08/20 16:56:03]

This is a release build so an SkASSERT would disapppear anyway right?

+    for (int i = 0; i < numWindows; ++i) {
         glwindows[i].setRelativeTo(rt->getViewport(), skwindows[i], rt->origin());
     }
 
     GrGLenum glmode = (Mode::kExclusive == windows.mode()) ? GR_GL_EXCLUSIVE : GR_GL_INCLUSIVE;
-    GL_CALL(WindowRectangles(glmode, windows.count(), glwindows->asInts()));
+    GL_CALL(WindowRectangles(glmode, numWindows, glwindows->asInts()));
 
     fHWWindowRects.set(rt->origin(), rt->getViewport(), windows);
 }