update example

src/views/SkWindow.cpp

Index: src/views/SkWindow.cpp
diff --git a/src/views/SkWindow.cpp b/src/views/SkWindow.cpp
index 7870d06bfe969a2105e2d379a53aee0ec63db7ce..61eaa978b15dc92d7b0f3009eeda25ea617244f1 100644
--- a/src/views/SkWindow.cpp
+++ b/src/views/SkWindow.cpp
@@ -341,3 +341,26 @@ bool SkWindow::onDispatchClick(int x, int y, Click::State state,
     }
     return handled;
 }
+
+#if SK_SUPPORT_GPU
+
+#include "gl/GrGLInterface.h"
+#include "gl/GrGLUtil.h"
+#include "SkGr.h"
+
+GrRenderTarget* SkWindow::renderTarget(const AttachmentInfo& attachmentInfo,
+        const GrGLInterface* interface, GrContext* grContext) {
+    GrBackendRenderTargetDesc desc;
+    desc.fWidth = SkScalarRoundToInt(this->width());
+    desc.fHeight = SkScalarRoundToInt(this->height());
+    desc.fConfig = kSkia8888_GrPixelConfig;
+    desc.fOrigin = kBottomLeft_GrSurfaceOrigin;
+    desc.fSampleCnt = attachmentInfo.fSampleCount;

[bsalomon, 2015/01/30 19:19:12]

The division of labor for creating a GL context, a GrContext, and a
GrRenderTarget* for the window's surface has evolved quite oddly. I think this
mostly has to do with Ganesh originally being born outside of Skia and Skia
wanting to use GL without depending on Ganesh, but being able to interop with
Ganesh when they were compiled together. Of course, that division is long gone.

What if Sk(OS)Window::attach() created all three and kept a ref to the GrContext
and GrRenderTarget? We might be able to eliminate AttachmentInfo and the need to
query the current FBO binding using glGetIntegerv. It could just wrap the
window's surface with a GrRenderTarget while creating the GL context.

[caryclark, 2015/01/30 19:55:28]

Sounds like a great idea, but refactoring SkOSWindow::attach() looks hard, or at
least worthy of its own CL. Each platform's implementation has little in common
-- not even C++.

+    desc.fStencilBits = attachmentInfo.fStencilBits;
+    GrGLint buffer;
+    GR_GL_GetIntegerv(interface, GR_GL_FRAMEBUFFER_BINDING, &buffer);
+    desc.fRenderTargetHandle = buffer;
+    return grContext->wrapBackendRenderTarget(desc);
+}
+
+#endif