Fiddle: update to new const GrGLAssembleInterface API

experimental/fiddle/fiddle_main.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include <stdio.h>
 
 #include <GL/osmesa.h>
@@ skipping 54 matching lines @@
 static OSMesaContext create_osmesa_context() {
     OSMesaContext osMesaContext =
         OSMesaCreateContextExt(OSMESA_BGRA, 0, 0, 0, nullptr);
     if (osMesaContext != nullptr) {
         static uint32_t buffer[16 * 16];
         OSMesaMakeCurrent(osMesaContext, &buffer, GL_UNSIGNED_BYTE, 16, 16);
     }
     return osMesaContext;
 }
 
-static GrContext* create_mesa_grcontext() {
-    sk_sp<const GrGLInterface> mesa(GrGLCreateMesaInterface());
-    intptr_t backend = reinterpret_cast<intptr_t>(mesa.get());
-    return backend ? GrContext::Create(kOpenGL_GrBackend, backend) : nullptr;
+static sk_sp<GrContext> create_mesa_grcontext() {
+    if (nullptr == OSMesaGetCurrentContext()) {
+        return nullptr;
+    }
+    auto osmesa_get = [](void* ctx, const char name[]) {
+        SkASSERT(nullptr == ctx);
+        SkASSERT(OSMesaGetCurrentContext());
+        return OSMesaGetProcAddress(name);
+    };
+    sk_sp<const GrGLInterface> mesa(GrGLAssembleInterface(nullptr, osmesa_get));
+    if (!mesa) {
+        return nullptr;
+    }
+    return sk_sp<GrContext>(GrContext::Create(
+                                    kOpenGL_GrBackend,
+                                    reinterpret_cast<intptr_t>(mesa.get())));
 }
 
-
 int main() {
     const DrawOptions options = GetDrawOptions();
     if (options.source) {
         sk_sp<SkData> data(SkData::NewFromFileName(options.source));
         if (!data) {
             perror(options.source);
             return 1;
         } else {
             image = SkImage::NewFromEncoded(data.get());
             if (!image) {
                 perror("Unable to decode the source image.");
                 return 1;
             }
             SkAssertResult(image->asLegacyBitmap(
                                    &source, SkImage::kRO_LegacyBitmapMode));
         }
     }
     sk_sp<SkData> rasterData, gpuData, pdfData, skpData;
     if (options.raster) {
         auto rasterSurface =
                 SkSurface::MakeRaster(SkImageInfo::MakeN32Premul(options.size));
         draw(rasterSurface->getCanvas());
         rasterData.reset(encode_snapshot(rasterSurface));
     }
     if (options.gpu) {
         OSMesaContext osMesaContext = create_osmesa_context();
-        sk_sp<GrContext> grContext(create_mesa_grcontext());
+        auto grContext = create_mesa_grcontext();
         if (!grContext) {
             fputs("Unable to get Mesa GrContext.\n", stderr);
         } else {
             auto surface = SkSurface::MakeRenderTarget(
                     grContext.get(),
                     SkBudgeted::kNo,
                     SkImageInfo::MakeN32Premul(options.size));
             if (!surface) {
                 fputs("Unable to get render surface.\n", stderr);
                 exit(1);
@@ skipping 26 matching lines @@
     printf("{\n");
     dump_output(rasterData, "Raster", !gpuData && !pdfData && !skpData);
     dump_output(gpuData, "Gpu", !pdfData && !skpData);
     dump_output(pdfData, "Pdf", !skpData);
     dump_output(skpData, "Skp");
     printf("}\n");
 
     SkSafeSetNull(image);
     return 0;
 }