blink: Enable test/experiment features before initilization.

Some of the blink initialization code can depend on test/experimental features.
So enable the features before blink::initialize()

BUG=436932

Review URL: https://codereview.chromium.org/1171853003

Cr-Commit-Position: refs/heads/master@{#333726}

content/renderer/render_view_browsertest.cc

@@ -147,11 +147,11 @@ class RenderViewImplTest : public RenderViewTest {
   ~RenderViewImplTest() override {}
 
   void SetUp() override {
-    RenderViewTest::SetUp();
     // Enable Blink's experimental and test only features so that test code
     // does not have to bother enabling each feature.
     WebRuntimeFeatures::enableExperimentalFeatures(true);
     WebRuntimeFeatures::enableTestOnlyFeatures(true);
+    RenderViewTest::SetUp();
   }
 
   RenderViewImpl* view() {