Use OS_LINUX instead of USE_OZONE in ui/gfx/ when possible

ui/gfx/mojo/struct_traits_unittest.cc

 // Copyright 2016 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 "base/message_loop/message_loop.h"
 #include "mojo/public/cpp/bindings/binding_set.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gfx/mojo/traits_test_service.mojom.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/selection_bound.h"
@@ skipping 148 matching lines @@
   gfx::GpuMemoryBufferHandle output;
   proxy->EchoGpuMemoryBufferHandle(handle, &output);
   EXPECT_EQ(gfx::SHARED_MEMORY_BUFFER, output.type);
   EXPECT_EQ(kId, output.id);
   EXPECT_EQ(kOffset, output.offset);
   EXPECT_EQ(kStride, output.stride);
 
   base::SharedMemory output_memory(output.handle, true);
   EXPECT_TRUE(output_memory.Map(1024));
 
-#if defined(USE_OZONE)
+#if defined(OS_LINUX)
   const uint64_t kSize = kOffset + kStride;
   const uint64_t kModifier = 2;
   handle.type = gfx::OZONE_NATIVE_PIXMAP;
   handle.id = kId;
   handle.native_pixmap_handle.planes.emplace_back(kOffset, kStride, kSize,
                                                   kModifier);
   proxy->EchoGpuMemoryBufferHandle(handle, &output);
   EXPECT_EQ(gfx::OZONE_NATIVE_PIXMAP, output.type);
   EXPECT_EQ(kId, output.id);
   ASSERT_EQ(1u, output.native_pixmap_handle.planes.size());
   EXPECT_EQ(kSize, output.native_pixmap_handle.planes.back().size);
   EXPECT_EQ(kModifier, output.native_pixmap_handle.planes.back().modifier);
 #endif
 }
 
 TEST_F(StructTraitsTest, NullGpuMemoryBufferHandle) {
   mojom::TraitsTestServicePtr proxy = GetTraitsTestProxy();
   GpuMemoryBufferHandle output;
   proxy->EchoGpuMemoryBufferHandle(GpuMemoryBufferHandle(), &output);
   EXPECT_TRUE(output.is_null());
 }
 
 }  // namespace gfx