Reland of Initialize default audio device ID with explicit device ID.

extensions/browser/guest_view/web_view/web_view_media_access_apitest.cc

 // Copyright 2014 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 "base/command_line.h"
 #include "base/macros.h"
 #include "base/strings/stringprintf.h"
 #include "content/public/browser/web_contents_delegate.h"
 #include "content/public/test/browser_test_utils.h"
 #include "extensions/browser/guest_view/web_view/web_view_apitest.h"
 #include "extensions/test/extension_test_message_listener.h"
 
 namespace {
 
 // This class intercepts media access request from the embedder. The request
@@ skipping 47 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(MockWebContentsDelegate);
 };
 
 }  // namespace
 
 namespace extensions {
 
 class WebViewMediaAccessAPITest : public WebViewAPITest {
  protected:
-  WebViewMediaAccessAPITest() {}
+  WebViewMediaAccessAPITest() {
+    // This switch ensures that there will always be at least one media device,
+    // even on machines without physical devices. This is required for tests
+    // that request permission to use media devices.
+    base::CommandLine::ForCurrentProcess()->AppendSwitch(

[Marijn Kruisselbrink, 2017/04/11 18:02:17]

nit: To add command line flags you should probably override SetUpCommandLine
(make sure you still call WebViewAPITest::SetUpCommandLine as well of course),
rather than doing this in the constructor.

+        "use-fake-device-for-media-stream");
+  }
 
   // Runs media_access tests.
   void RunTest(const std::string& test_name) {
     ExtensionTestMessageListener test_run_listener("TEST_PASSED", false);
     test_run_listener.set_failure_message("TEST_FAILED");
     EXPECT_TRUE(content::ExecuteScript(
         embedder_web_contents_,
         base::StringPrintf("runTest('%s');", test_name.c_str())));
     ASSERT_TRUE(test_run_listener.WaitUntilSatisfied());
   }
@@ skipping 109 matching lines @@
                        TestNoPreventDefaultImpliesDeny) {
   std::string app_location = "web_view/media_access/deny";
   StartTestServer(app_location);
   LaunchApp(app_location);
 
   RunTest("testNoPreventDefaultImpliesDeny");
   StopTestServer();
 }
 
 }  // namespace extensions