Add virtual layout test for GPU accelerated decoding.

third_party/WebKit/LayoutTests/VirtualTestSuites

Index: third_party/WebKit/LayoutTests/VirtualTestSuites
diff --git a/third_party/WebKit/LayoutTests/VirtualTestSuites b/third_party/WebKit/LayoutTests/VirtualTestSuites
index 976ec13bf5a14e7d560e18739929c403dcf976b5..d6855e9b766f584888266ff914ea381a396f73d6 100644
--- a/third_party/WebKit/LayoutTests/VirtualTestSuites
+++ b/third_party/WebKit/LayoutTests/VirtualTestSuites
@@ -93,6 +93,11 @@
              "--disable-composited-antialiasing"]
   },
   {
+    "prefix": "media-gpu-accelerated",
+    "base": "http/tests/media/media-source",
+    "args": ["--use-gpu-in-tests"]
+  },
+  {
     "prefix": "android",
     "base": "media/mediadocument",
     "args": ["--enable-features=MediaDocumentDownloadButton"]