media/gpu/test: Fix DCHECK using ScopedFeatureList

Only one ScopedFeatureList::InitXXX function should be called on
a particular ScopedFeatureList instance. If any Init functions are
called more than once, it will hit DCHECK(!init_called_) in
ScopedFeatureList::InitWithFeaturesImpl.

Refactor feature enabling so that the desired features are sent as
a vector of features in one call to ScopedFeatureList::InitWithFeatures

TEST=video_encode_accelerator_unittest does not hit DCHECK
BUG=none

Change-Id: I445ea51740b93361c771450e47cd31300ae13c69
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1862257Reviewed-by: Miguel Casas <mcasas@chromium.org>
Commit-Queue: Drew Davenport <ddavenport@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706126}

media/gpu/video_encode_accelerator_unittest.cc

@@ -3115,11 +3115,13 @@ class VEATestSuite : public base::TestSuite {
 
 #if BUILDFLAG(USE_VAAPI)
     base::test::ScopedFeatureList scoped_feature_list;
-    // TODO(crbug.com/811912): remove once enabled by default.
-    scoped_feature_list.InitAndEnableFeature(media::kVaapiVP9Encoder);
-    // TODO(crbug.com/828482): Remove once H264 encoder on AMD is enabled by
-    // default.
-    scoped_feature_list.InitAndEnableFeature(media::kVaapiH264AMDEncoder);
+    std::vector<base::Feature> enabled_features = {
+        // TODO(crbug.com/811912): remove once enabled by default.
+        media::kVaapiVP9Encoder,
+        // TODO(crbug.com/828482): Remove once H264 encoder on AMD is enabled by
+        // default.
+        media::kVaapiH264AMDEncoder};
+    scoped_feature_list.InitWithFeatures(enabled_features, {});
     media::VaapiWrapper::PreSandboxInitialization();
 #elif defined(OS_WIN)
     media::MediaFoundationVideoEncodeAccelerator::PreSandboxInitialization();