Refactor OS_LINUX preprocessor directive for LaCrOS effort.

Currently, ChromeOS defines the OS_LINUX directive as well as
OS_CHROMEOS.  We're working to separate these two, so we're
making the fact that OS_LINUX == OS_LINUX || OS_CHROMEOS
explicit.

This is changes for /media/video/fake_gpu_memory_buffer.cc

This CL was uploaded by git cl split.

R=dcastagna@chromium.org

Bug: 1110266
Change-Id: I96e84181f4cdb58d754759abb18a08a00fdc74a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2370730Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Commit-Queue: Sean McAllister <smcallis@google.com>
Cr-Commit-Position: refs/heads/master@{#801397}

media/video/fake_gpu_memory_buffer.cc

@@ -10,7 +10,7 @@
 #include "media/base/format_utils.h"
 #include "media/base/video_frame.h"
 
-#if defined(OS_LINUX)
+#if defined(OS_LINUX) || defined(OS_CHROMEOS)
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -48,7 +48,7 @@ class FakeGpuMemoryBufferImpl : public gpu::GpuMemoryBufferImpl {
 
 }  // namespace
 
-#if defined(OS_LINUX)
+#if defined(OS_LINUX) || defined(OS_CHROMEOS)
 base::ScopedFD GetDummyFD() {
   base::ScopedFD fd(open("/dev/zero", O_RDWR));
   DCHECK(fd.is_valid());
@@ -73,7 +73,7 @@ FakeGpuMemoryBuffer::FakeGpuMemoryBuffer(const gfx::Size& size,
   static base::NoDestructor<base::AtomicSequenceNumber> buffer_id_generator;
   handle_.id = gfx::GpuMemoryBufferId(buffer_id_generator->GetNext());
 
-#if defined(OS_LINUX)
+#if defined(OS_LINUX) || defined(OS_CHROMEOS)
   for (size_t i = 0; i < VideoFrame::NumPlanes(video_pixel_format_); i++) {
     const gfx::Size plane_size_in_bytes =
         VideoFrame::PlaneSize(video_pixel_format_, i, size_);
@@ -81,7 +81,7 @@ FakeGpuMemoryBuffer::FakeGpuMemoryBuffer(const gfx::Size& size,
         plane_size_in_bytes.width(), 0, plane_size_in_bytes.GetArea(),
         GetDummyFD());
   }
-#endif  // defined(OS_LINUX)
+#endif  // defined(OS_LINUX) || defined(OS_CHROMEOS)
 }
 
 FakeGpuMemoryBuffer::~FakeGpuMemoryBuffer() = default;
@@ -129,7 +129,7 @@ gfx::GpuMemoryBufferHandle FakeGpuMemoryBuffer::CloneHandle() const {
   gfx::GpuMemoryBufferHandle handle;
   handle.type = gfx::NATIVE_PIXMAP;
   handle.id = handle_.id;
-#if defined(OS_LINUX)
+#if defined(OS_LINUX) || defined(OS_CHROMEOS)
   handle.native_pixmap_handle =
       gfx::CloneHandleForIPC(handle_.native_pixmap_handle);
 #endif