Improve usage of window rectangles

src/gpu/GrWindowRectsState.h

Index: src/gpu/GrWindowRectsState.h
diff --git a/src/gpu/GrWindowRectsState.h b/src/gpu/GrWindowRectsState.h
new file mode 100644
index 0000000000000000000000000000000000000000..9d3b61b9cb350aa513e28683d7b8927f19b863c1
--- /dev/null
+++ b/src/gpu/GrWindowRectsState.h
@@ -0,0 +1,60 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrWindowRectsState_DEFINED
+#define GrWindowRectsState_DEFINED
+
+#include "GrWindowRectangles.h"
+
+class GrWindowRectsState {
+public:
+    enum class Mode : bool {
+        kExclusive,
+        kInclusive
+    };
+
+    GrWindowRectsState() : fMode(Mode::kExclusive) {}
+    GrWindowRectsState(const GrWindowRectangles& windows, const SkIPoint& origin, Mode mode)
+        : fMode(mode)
+        , fOrigin(origin)
+        , fWindows(windows) {
+    }
+
+    bool enabled() const { return Mode::kInclusive == fMode || !fWindows.empty(); }
+    Mode mode() const { return fMode; }
+    const SkIPoint& origin() const { return fOrigin; }
+    const GrWindowRectangles& windows() const { return fWindows; }
+    int numWindows() const { return fWindows.count(); }
+
+    void setDisabled() {
+        fMode = Mode::kExclusive;
+        fWindows.reset();
+    }
+
+    void set(const GrWindowRectangles& windows, const SkIPoint& origin, Mode mode) {
+        fMode = mode;
+        fOrigin = origin;
+        fWindows = windows;
+    }
+
+    bool cheapEqualTo(const GrWindowRectsState& that) const {
+        if (fMode != that.fMode) {
+            return false;
+        }
+        if (!fWindows.empty() && fOrigin != that.fOrigin) {
+            return false;
+        }
+        return fWindows == that.fWindows;
+    }
+
+private:
+    Mode                 fMode;
+    SkIPoint             fOrigin;
+    GrWindowRectangles   fWindows;
+};
+
+#endif