Use a struct for client GL texture handles

tests/GrPorterDuffTest.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 "SkXfermode.h"
 #include "Test.h"
 
@@ skipping 1146 matching lines @@
         SkFAIL("Failed to create null context without ARB_blend_func_extended.");
         return;
     }
 
     const GrCaps& caps = *ctx->caps();
     if (caps.shaderCaps()->dualSourceBlendingSupport()) {
         SkFAIL("Null context failed to honor request for no ARB_blend_func_extended.");
         return;
     }
 
+    GrBackendObject backendTex =
+        ctx->getGpu()->createTestingOnlyBackendTexture(nullptr, 100, 100, kRGBA_8888_GrPixelConfig);
     GrBackendTextureDesc fakeDesc;
     fakeDesc.fConfig = kRGBA_8888_GrPixelConfig;
     fakeDesc.fWidth = fakeDesc.fHeight = 100;
-    fakeDesc.fTextureHandle = 1;
+    fakeDesc.fTextureHandle = backendTex;
     SkAutoTUnref<GrTexture> fakeTexture(ctx->textureProvider()->wrapBackendTexture(fakeDesc,
         kBorrow_GrWrapOwnership));
     GrXferProcessor::DstTexture fakeDstTexture;
     fakeDstTexture.setTexture(fakeTexture);
 
     static const GrColor testColors[] = {
         0,
         GrColorPackRGBA(0, 82, 0, 255),
         GrColorPackA4(255)
     };
@@ skipping 25 matching lines @@
                 if (!xp) {
                     ERRORF(reporter, "Failed to create an XP without dual source blending.");
                     return;
                 }
                 TEST_ASSERT(!xp->hasSecondaryOutput());
                 xp->getOptimizations(colorPOI, covPOI, false, 0, caps);
                 TEST_ASSERT(!xp->hasSecondaryOutput());
             }
         }
     }
+    ctx->getGpu()->deleteTestingOnlyBackendTexture(backendTex);
 }
 
 #endif