Add sRGB mode toggle to Viewer.

tools/viewer/sk_app/Window.cpp

Index: tools/viewer/sk_app/Window.cpp
diff --git a/tools/viewer/sk_app/Window.cpp b/tools/viewer/sk_app/Window.cpp
index a7fd6b0cf67d95a07042747142e2fd5580a0d5bf..e557ffce61f9624a6401c8c0f10f6ef7d260ba10 100644
--- a/tools/viewer/sk_app/Window.cpp
+++ b/tools/viewer/sk_app/Window.cpp
@@ -75,4 +75,12 @@ void Window::onResize(uint32_t w, uint32_t h) {
     fWindowContext->resize(w, h);
 }
 
+bool Window::getSRGB() {
+    return fWindowContext->getSRGB();
+}
+
+void Window::setSRGB(bool srgb) {
+    fWindowContext->setSRGB(srgb);
+}
+
 }   // namespace sk_app