Centralize mojo edk initialization path for some unit tests.

content/test/test_blink_web_unit_test_support.cc

Index: content/test/test_blink_web_unit_test_support.cc
diff --git a/content/test/test_blink_web_unit_test_support.cc b/content/test/test_blink_web_unit_test_support.cc
index 6ffcac0dd5e71ba8edd574363438822e98d27935..52c9db2e589722a361680463be387af6a28f0dfb 100644
--- a/content/test/test_blink_web_unit_test_support.cc
+++ b/content/test/test_blink_web_unit_test_support.cc
@@ -19,6 +19,7 @@
 #include "cc/blink/web_layer_impl.h"
 #include "cc/test/test_shared_bitmap_manager.h"
 #include "cc/trees/layer_tree_settings.h"
+#include "content/app/mojo/mojo_init.h"
 #include "content/child/web_url_loader_impl.h"
 #include "content/test/mock_webclipboard_impl.h"
 #include "content/test/web_gesture_curve_mock.h"
@@ -124,6 +125,9 @@ TestBlinkWebUnitTestSupport::TestBlinkWebUnitTestSupport() {
   // an error that it's not set. Cleared by ClearInstanceForTesting() below.
   base::FeatureList::SetInstance(base::WrapUnique(new base::FeatureList));
 
+  // Initialize mojo firstly to enable Blink initialization to use it.
+  InitializeMojo();
+
   blink::initialize(this);
   blink::setLayoutTestMode(true);
   blink::WebRuntimeFeatures::enableDatabase(true);