Setting chrome as the default browser is now fixed on Windows 10

chrome/browser/custom_handlers/protocol_handler_registry_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/custom_handlers/protocol_handler_registry.h"
 
 #include <set>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 208 matching lines @@
  public:
   FakeProtocolClientWorker(ShellIntegration::DefaultWebClientObserver* observer,
                            const std::string& protocol,
                            bool force_failure)
       : ShellIntegration::DefaultProtocolClientWorker(observer, protocol),
         force_failure_(force_failure) {}
 
  private:
   ~FakeProtocolClientWorker() override {}
 
-  ShellIntegration::DefaultWebClientState CheckIsDefault() override {
-    if (force_failure_) {
-      return ShellIntegration::NOT_DEFAULT;
-    } else {
-      return ShellIntegration::IS_DEFAULT;
-    }
+  void CheckIsDefault() override {
+    ShellIntegration::DefaultWebClientState state =
+        ShellIntegration::IS_DEFAULT;
+    if (force_failure_)
+      state = ShellIntegration::NOT_DEFAULT;
+
+    BrowserThread::PostTask(
+        BrowserThread::UI, FROM_HERE,
+        base::Bind(&FakeProtocolClientWorker::OnCheckIsDefaultComplete, this,
+                   state));
   }
 
-  bool SetAsDefault(bool interactive_permitted) override { return true; }
+  void SetAsDefault(bool interactive_permitted) override {
+    BrowserThread::PostTask(
+        BrowserThread::UI, FROM_HERE,
+        base::Bind(&FakeProtocolClientWorker::OnSetAsDefaultAttemptComplete,
+                   this, AttemptResult::SUCCESS));
+  }
 
  private:
   bool force_failure_;
 };
 
 ProtocolHandlerRegistry::DefaultClientObserver*
     FakeDelegate::CreateShellObserver(ProtocolHandlerRegistry* registry) {
   return new FakeClientObserver(registry, this);
 }
 
@@ skipping 874 matching lines @@
   // added to pref.
   ASSERT_EQ(InPrefIgnoredHandlerCount(), 2);
   ASSERT_EQ(InMemoryIgnoredHandlerCount(), 4);
 
   registry()->RemoveIgnoredHandler(p2u1);
 
   // p2u1 installed by user and policy, so it is removed from pref alone.
   ASSERT_EQ(InPrefIgnoredHandlerCount(), 1);
   ASSERT_EQ(InMemoryIgnoredHandlerCount(), 4);
 }