Avoid creating full screen clear batches when there is already one in the queue.

src/gpu/batches/GrClearBatch.h

Index: src/gpu/batches/GrClearBatch.h
diff --git a/src/gpu/batches/GrClearBatch.h b/src/gpu/batches/GrClearBatch.h
index 00a1c84de653cfb5d811fb2c2374444be990286a..8ebf85af2e882abf7b06ce7aa0c287b63db35e87 100644
--- a/src/gpu/batches/GrClearBatch.h
+++ b/src/gpu/batches/GrClearBatch.h
@@ -18,8 +18,8 @@ class GrClearBatch final : public GrBatch {
 public:
     DEFINE_BATCH_CLASS_ID
 
-    static sk_sp<GrBatch> Make(const SkIRect& rect,  GrColor color, GrRenderTarget* rt) {
-        return sk_sp<GrBatch>(new GrClearBatch(rect, color, rt));
+    static sk_sp<GrClearBatch> Make(const SkIRect& rect,  GrColor color, GrRenderTarget* rt) {
+        return sk_sp<GrClearBatch>(new GrClearBatch(rect, color, rt));
     }
 
     const char* name() const override { return "Clear"; }
@@ -36,6 +36,8 @@ public:
         return string;
     }
 
+    void setColor(GrColor color) { fColor = color; }
+
 private:
     GrClearBatch(const SkIRect& rect,  GrColor color, GrRenderTarget* rt)
         : INHERITED(ClassID())