Make webkit_unit_tests support --enable-blink-features

(Also --disable-blink-features)

We would like to use this to run the tests with LayoutNG enabled.

Change-Id: I1c8909dc3e1aaa57dc6745624ba6f8170ccde7e5
Reviewed-on: https://chromium-review.googlesource.com/c/1329884Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607129}

content/public/test/blink_test_environment.cc

@@ -13,6 +13,7 @@
 #include "base/test/scoped_task_environment.h"
 #include "base/test/test_discardable_memory_allocator.h"
 #include "build/build_config.h"
+#include "content/common/content_switches_internal.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/user_agent.h"
 #include "content/public/test/test_content_client_initializer.h"
@@ -70,6 +71,17 @@ void SetUpBlinkTestEnvironment() {
   blink::WebRuntimeFeatures::EnableExperimentalFeatures(true);
   blink::WebRuntimeFeatures::EnableTestOnlyFeatures(true);
 
+  const base::CommandLine& command_line =
+      *base::CommandLine::ForCurrentProcess();
+  for (const std::string& feature : content::FeaturesFromSwitch(
+           command_line, switches::kEnableBlinkFeatures)) {
+    blink::WebRuntimeFeatures::EnableFeatureFromString(feature, true);
+  }
+  for (const std::string& feature : content::FeaturesFromSwitch(
+           command_line, switches::kDisableBlinkFeatures)) {
+    blink::WebRuntimeFeatures::EnableFeatureFromString(feature, false);
+  }
+
 #if defined(OS_MACOSX)
   mock_cr_app::RegisterMockCrApp();
 #endif