gfx: Use unsigned strides for gpu memory buffers.

gpu/command_buffer/tests/gl_gpu_memory_buffer_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <GLES2/gl2.h>
 #include <GLES2/gl2chromium.h>
 #include <GLES2/gl2ext.h>
 #include <GLES2/gl2extchromium.h>
 #include <stdint.h>
 
@@ skipping 170 matching lines @@
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
 
   // Create the gpu memory buffer.
   std::unique_ptr<gfx::GpuMemoryBuffer> buffer(gl_.CreateGpuMemoryBuffer(
       gfx::Size(kImageWidth, kImageHeight), GetParam()));
 
   // Map buffer for writing.
   ASSERT_TRUE(buffer->Map());
   ASSERT_NE(nullptr, buffer->memory(0));
-  ASSERT_NE(0, buffer->stride(0));
+  ASSERT_NE(0u, buffer->stride(0));
   uint8_t pixel[] = {255u, 0u, 0u, 255u};
 
   // Assign a value to each pixel.
   for (int y = 0; y < kImageHeight; ++y) {
     SetRow(GetParam(),
            static_cast<uint8_t*>(buffer->memory(0)) + y * buffer->stride(0),
            kImageWidth, pixel);
   }
   // Unmap the buffer.
   buffer->Unmap();
@@ skipping 47 matching lines @@
 INSTANTIATE_TEST_CASE_P(GpuMemoryBufferTests,
                         GpuMemoryBufferTest,
                         ::testing::Values(gfx::BufferFormat::R_8,
                                           gfx::BufferFormat::BGR_565,
                                           gfx::BufferFormat::RGBA_4444,
                                           gfx::BufferFormat::RGBA_8888,
                                           gfx::BufferFormat::BGRA_8888));
 
 }  // namespace gles2
 }  // namespace gpu