Add functionality to get default media device IDs from user preferences.

chrome/browser/ui/browser_browsertest.cc

 // Copyright 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/ui/browser.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
@@ skipping 2737 matching lines @@
   // destroy |contents|.
   interstitial->DontProceed();
   content::WaitForInterstitialDetach(web_contents);
   // interstitial is deleted now.
 
   EXPECT_TRUE(chrome::CanDuplicateTab(browser()));
   EXPECT_TRUE(chrome::CanDuplicateTabAt(browser(), 0));
   EXPECT_TRUE(chrome::CanDuplicateTabAt(browser(), 1));
 }
 
+IN_PROC_BROWSER_TEST_F(BrowserTest, DefaultMediaDevices) {
+  std::string default_audio_capture_1("test_default_audio_capture");

[Peter Kasting, 2017/01/24 00:39:17]

Nit: Prefer = to () for initializing strings; see
https://www.chromium.org/developers/coding-style/cpp-dos-and-donts#TOC-Variab...
(several places)

Consider using const and naming these kConstantStyle, since these are
compile-time constants.  (Can't use constexpr with std::string.)

[Guido Urdaneta, 2017/01/24 09:31:35]

Done.

+  std::string default_video_capture_1("test_default_video_capture");
+  browser()->profile()->GetPrefs()->SetString(prefs::kDefaultAudioCaptureDevice,
+                                              default_audio_capture_1);
+  browser()->profile()->GetPrefs()->SetString(prefs::kDefaultVideoCaptureDevice,
+                                              default_video_capture_1);

[Peter Kasting, 2017/01/24 00:39:17]

Nit: Optional, but if you use a lambda here, you can reduce the boilerplate in
these SetString() calls:

  auto SetString = [this](const std::string& path, const std::string& value) {
    browser()->profile()->GetPrefs()->SetString(path, value);
  }
  SetString(prefs::kDefaultAudioCaptureDevice, default_audio_capture_1);
  ...

(overall this is one line shorter)

[Guido Urdaneta, 2017/01/24 09:31:35]

Done.

+  ui_test_utils::NavigateToURL(browser(), GURL("chrome://newtab"));
+  WebContents* web_contents =
+      browser()->tab_strip_model()->GetActiveWebContents();
+  EXPECT_EQ(default_audio_capture_1,
+            web_contents->GetDelegate()->GetDefaultMediaDeviceID(
+                web_contents, content::MEDIA_DEVICE_AUDIO_CAPTURE));

[Peter Kasting, 2017/01/24 00:39:17]

Nit: Optional, but if you use a lambda here, you can reduce the boilerplate in
these EXPECTs:

  auto GetDeviceID = [web_contents](content::MediaStreamType type) {
    return web_contents->GetDelegate()->GetDefaultMediaDeviceID(web_contents,
                                                                type);
  }
  EXPECT_EQ(default_audio_capture_1,
            GetDeviceID(content::MEDIA_DEVICE_AUDIO_CAPTURE));
  ...

(overall this is the same number of lines)

[Guido Urdaneta, 2017/01/24 09:31:35]

Done.

+  EXPECT_EQ(default_video_capture_1,
+            web_contents->GetDelegate()->GetDefaultMediaDeviceID(
+                web_contents, content::MEDIA_DEVICE_VIDEO_CAPTURE));
+
+  std::string default_audio_capture_2("test_default_audio_capture_2");
+  std::string default_video_capture_2("test_default_video_capture_2");
+  browser()->profile()->GetPrefs()->SetString(prefs::kDefaultAudioCaptureDevice,
+                                              default_audio_capture_2);
+  browser()->profile()->GetPrefs()->SetString(prefs::kDefaultVideoCaptureDevice,
+                                              default_video_capture_2);
+  EXPECT_EQ(default_audio_capture_2,
+            web_contents->GetDelegate()->GetDefaultMediaDeviceID(
+                web_contents, content::MEDIA_DEVICE_AUDIO_CAPTURE));
+  EXPECT_EQ(default_video_capture_2,
+            web_contents->GetDelegate()->GetDefaultMediaDeviceID(
+                web_contents, content::MEDIA_DEVICE_VIDEO_CAPTURE));
+}
+
 namespace {
 class JSBooleanResultGetter {
  public:
   JSBooleanResultGetter() = default;
   void OnJsExecutionDone(base::Closure callback, const base::Value* value) {
     js_result_.reset(value->DeepCopy());
     callback.Run();
   }
   bool GetResult() const {
     bool res;
@@ skipping 134 matching lines @@
     Browser* browser = new Browser(params);
     gfx::Rect bounds = browser->window()->GetBounds();
 
     // Should be EXPECT_EQ, but this width is inconsistent across platforms.
     // See https://crbug.com/567925.
     EXPECT_GE(bounds.width(), 100);
     EXPECT_EQ(122, bounds.height());
     browser->window()->Close();
   }
 }