Set GL_PACK_ALIGNMENT before calling glReadPixels

tests/ReadWriteAlphaTest.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Test.h"
 
 // This test is specific to the GPU backend.
 #if SK_SUPPORT_GPU && !defined(SK_BUILD_FOR_ANDROID)
 
 #include "GrContext.h"
 #include "SkGpuDevice.h"
 
-static const int X_SIZE = 12;
-static const int Y_SIZE = 12;
+// This was made indivisible by 4 to ensure we test setting GL_PACK_ALIGNMENT properly.
+static const int X_SIZE = 13;
+static const int Y_SIZE = 13;
 
 DEF_GPUTEST_FOR_RENDERING_CONTEXTS(ReadWriteAlpha, reporter, context) {
     unsigned char textureData[X_SIZE][Y_SIZE];
 
     memset(textureData, 0, X_SIZE * Y_SIZE);
 
     GrSurfaceDesc desc;
 
     // let Skia know we will be using this texture as a render target
     desc.fFlags     = kRenderTarget_GrSurfaceFlag;
@@ skipping 67 matching lines @@
             if (0xFF != readback[x][y]) {
                 match = false;
             }
         }
     }
 
     REPORTER_ASSERT(reporter, match);
 }
 
 #endif