Implement Raster Backend on Android Viewer App

tools/viewer/sk_app/RasterWindowContext.cpp

Index: tools/viewer/sk_app/RasterWindowContext.cpp
diff --git a/tools/viewer/sk_app/RasterWindowContext.cpp b/tools/viewer/sk_app/RasterWindowContext.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..5bb1d2da1fad420a7a41dbce7c3c5217f1d5a979
--- /dev/null
+++ b/tools/viewer/sk_app/RasterWindowContext.cpp
@@ -0,0 +1,37 @@
+
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "RasterWindowContext.h"
+
+#include "SkSurface.h"
+
+namespace sk_app {
+
+sk_sp<SkSurface> RasterWindowContext::getBackbufferSurface() {
+    if (nullptr == fBackbufferSurface) {
+        fBackbufferSurface = SkSurface::MakeRaster(this->getImageInfo(), 0, nullptr);
+    }
+    return fBackbufferSurface;
+}
+
+// Somehow, I couldn't make this a field for reuse.
+// Weird things happen as soon as I declare a SkImageInfo field...
+SkImageInfo RasterWindowContext::getImageInfo() {
+    return SkImageInfo::Make(fWidth, fHeight,
+                             fDisplayParams.fColorType,
+                             kOpaque_SkAlphaType,
+                             fDisplayParams.fProfileType);
+}
+
+void RasterWindowContext::swapBuffers() {
+    sk_sp<SkImage> image = fBackbufferSurface->makeImageSnapshot();
+    this->onSwapBuffers(image);
+    fBackbufferSurface.reset(nullptr);
+}
+
+}   // namespace sk_app