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..83d2df29bfdb81a4c21540604a4c4d9dc1e55c58 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -2004,17 +2004,21 @@ void GrGLGpu::flushWindowRectangles(const GrWindowRectangles& windows, const GrG
     if (!this->caps()->maxWindowRectangles() ||
         fHWWindowRects.equal(rt->origin(), rt->getViewport(), windows)) {
         return;
-
     }
 
+    // This is purely a workaround for a spurious warning generated by gcc. Otherwise the above
+    // assert would be sufficient. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=5912
+    int numWindows = SkTMin(windows.count(), int(GrWindowRectangles::kMaxWindows));
+    SkASSERT(windows.count() == numWindows);
+
     GrGLIRect glwindows[GrWindowRectangles::kMaxWindows];
     const SkIRect* skwindows = windows.data();
-    for (int i = 0; i < windows.count(); ++i) {
+    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);
 }