Improve usage of window rectangles

src/gpu/vk/GrVkGpuCommandBuffer.cpp

Index: src/gpu/vk/GrVkGpuCommandBuffer.cpp
diff --git a/src/gpu/vk/GrVkGpuCommandBuffer.cpp b/src/gpu/vk/GrVkGpuCommandBuffer.cpp
index d7a030d24156bafa10e4c588480210db287af8bf..83e9cb17c72909d15ea26a487cf239bc917656ce 100644
--- a/src/gpu/vk/GrVkGpuCommandBuffer.cpp
+++ b/src/gpu/vk/GrVkGpuCommandBuffer.cpp
@@ -170,6 +170,7 @@ void GrVkGpuCommandBuffer::onClearStencilClip(GrRenderTarget* target,
                                               const GrFixedClip& clip,
                                               bool insideStencilMask) {
     SkASSERT(target);
+    SkASSERT(clip.windowRectangles().disabled());
 
     GrVkRenderTarget* vkRT = static_cast<GrVkRenderTarget*>(target);
     GrStencilAttachment* sb = target->renderTargetPriv().getStencilAttachment();
@@ -223,6 +224,7 @@ void GrVkGpuCommandBuffer::onClearStencilClip(GrRenderTarget* target,
 void GrVkGpuCommandBuffer::onClear(GrRenderTarget* target, const GrFixedClip& clip, GrColor color) {
     // parent class should never let us get here with no RT
     SkASSERT(target);
+    SkASSERT(clip.windowRectangles().disabled());
 
     VkClearColorValue vkColor;
     GrColorToRGBAFloat(color, vkColor.float32);