Only run test_wrapped_resources() when GL is active

tests/ResourceCacheTest.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 // Include here to ensure SK_SUPPORT_GPU is set correctly before it is examined.
 #include "SkTypes.h"
 
@@ skipping 158 matching lines @@
                         smallMSAART0->asRenderTarget() &&
                         smallMSAART1->asRenderTarget() &&
                         smallMSAART0->asRenderTarget()->renderTargetPriv().getStencilAttachment() !=
                         smallMSAART1->asRenderTarget()->renderTargetPriv().getStencilAttachment());
         }
     }
 }
 
 static void test_wrapped_resources(skiatest::Reporter* reporter, GrContext* context) {
     const GrGpu* gpu = context->getGpu();
-    if (!gpu) {
+    // this test is only valid for GL
+    if (!gpu || !gpu->glContextForTesting()) {
         return;
     }
 
     GrBackendObject texIDs[2];
     static const int kW = 100;
     static const int kH = 100;
 
     texIDs[0] = gpu->createTestingOnlyBackendTexture(NULL, kW, kH, kRGBA_8888_GrPixelConfig);
     texIDs[1] = gpu->createTestingOnlyBackendTexture(NULL, kW, kH, kRGBA_8888_GrPixelConfig);
 
@@ skipping 1067 matching lines @@
     test_scratch_key_consistency(reporter);
     test_purge_invalidated(reporter);
     test_cache_chained_purge(reporter);
     test_resource_size_changed(reporter);
     test_timestamp_wrap(reporter);
     test_flush(reporter);
     test_large_resource_count(reporter);
 }
 
 #endif