web-threads: Create a single instance of WebThread for each blink thread.

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 1bee8c053639a4ac4ec9670b050b86044058cf7e..81a0552b2ebddb2e8981356b68e17e0b99f289b0 100644
--- a/content/test/test_blink_web_unit_test_support.cc
+++ b/content/test/test_blink_web_unit_test_support.cc
@@ -13,6 +13,7 @@
 #include "content/public/common/content_switches.h"
 #include "content/renderer/scheduler/renderer_scheduler.h"
 #include "content/renderer/scheduler/web_scheduler_impl.h"
+#include "content/renderer/scheduler/webthread_impl_for_scheduler.h"
 #include "content/test/mock_webclipboard_impl.h"
 #include "content/test/web_gesture_curve_mock.h"
 #include "content/test/web_layer_tree_view_impl_for_testing.h"
@@ -60,6 +61,7 @@ TestBlinkWebUnitTestSupport::TestBlinkWebUnitTestSupport() {
   if (base::MessageLoopProxy::current()) {
     renderer_scheduler_ = RendererScheduler::Create();
     web_scheduler_.reset(new WebSchedulerImpl(renderer_scheduler_.get()));
+    web_thread_.reset(new WebThreadImplForScheduler(renderer_scheduler_.get()));
   }
 
   blink::initialize(this);
@@ -319,4 +321,10 @@ blink::WebScheduler* TestBlinkWebUnitTestSupport::scheduler() {
   return web_scheduler_.get();
 }
 
+blink::WebThread* TestBlinkWebUnitTestSupport::currentThread() {
+  if (web_thread_ && web_thread_->isCurrentThread())
+    return web_thread_.get();
+  return BlinkPlatformImpl::currentThread();
+}
+
 }  // namespace content