Add vaapi_h264_decoder_test.

content/content_tests.gypi

Index: content/content_tests.gypi
diff --git a/content/content_tests.gypi b/content/content_tests.gypi
index 6b6e17b611e2bb69d846e12856a86c18392e8695..ad3ebc795ae2eab8f32c9aa3eb5a1e76c6986bf7 100644
--- a/content/content_tests.gypi
+++ b/content/content_tests.gypi
@@ -1319,6 +1319,33 @@
           },
         ]
     }],
+    ['chromeos==1 and use_x11 == 1 and target_arch != "arm"', {
+      'targets': [
+          {
+            'target_name': 'vaapi_h264_decoder_unittest',
+            'type': '<(gtest_target_type)',
+            'dependencies': [
+              'content.gyp:content_common',
+              '../base/base.gyp:base',
+              '../media/media.gyp:media',
+              '../testing/gtest.gyp:gtest',
+              '../third_party/libyuv/libyuv.gyp:libyuv',
+              '../ui/gfx/gfx.gyp:gfx_geometry',
+            ],
+            'sources': [
+              'common/gpu/media/vaapi_h264_decoder_unittest.cc',
+            ],
+            'include_dirs': [
+              '<(DEPTH)/third_party/libva',
+            ],
+            'link_settings': {
+              'libraries': [
+                '-lX11',
+              ],
+            },
+          },
+        ]
+    }],
     ['chromeos==1 and target_arch == "arm"', {
       'targets': [
         {