chromeos_camera: Skip testing the shmem path for V4L2

We only use DMA buffer for V4L2 path, don't need to test them. For VAAPI
case, some older boards may use the shmem path so keep them.

Bug: b:171356989
Test: jpeg_encode_accelerator_unittest
Change-Id: I02b088925b088cbaf7597dddd3ac50835b27ab9a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2757593
Reviewed-by: Wei Lee <wtlee@chromium.org>
Commit-Queue: Hsu Wei-Cheng <mojahsu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#862730}

components/chromeos_camera/jpeg_encode_accelerator_unittest.cc

@@ -817,6 +817,9 @@ void JpegEncodeAcceleratorTest::TestEncode(size_t num_concurrent_encoders,
   VLOG(1) << "Exit TestEncode";
 }
 
+// We may need to keep the VAAPI shared memory path for Linux-based Chrome VCD.
+// Some of our older boards are still running on the Linux VCD.
+#if BUILDFLAG(USE_VAAPI)
 TEST_F(JpegEncodeAcceleratorTest, SimpleEncode) {
   for (size_t i = 0; i < g_env->repeat_; i++) {
     for (auto& image : g_env->image_data_user_) {
@@ -855,6 +858,7 @@ TEST_F(JpegEncodeAcceleratorTest, CodedSizeAlignment) {
   TestEncode(/*num_concurrent_encoders=*/1u, /*is_dma=*/false,
              /*exif_size=*/0u);
 }
+#endif
 
 TEST_F(JpegEncodeAcceleratorTest, SimpleDmaEncode) {
   for (size_t i = 0; i < g_env->repeat_; i++) {