content: Split out VideoCaptureMachine from DesktopCaptureDeviceAura

content/browser/media/capture/desktop_capture_device_aura.cc

Index: content/browser/media/capture/desktop_capture_device_aura.cc
diff --git a/content/browser/media/capture/desktop_capture_device_aura.cc b/content/browser/media/capture/desktop_capture_device_aura.cc
index 37979613dddf0572340bda84df472ae3df7c2033..741e4b8062a67bde891c60c623fd93c041e6b329 100644
--- a/content/browser/media/capture/desktop_capture_device_aura.cc
+++ b/content/browser/media/capture/desktop_capture_device_aura.cc
@@ -95,7 +95,7 @@ class DesktopVideoCaptureMachine
       public ui::CompositorObserver,
       public base::SupportsWeakPtr<DesktopVideoCaptureMachine> {
  public:
-  DesktopVideoCaptureMachine(const DesktopMediaID& source);
+  DesktopVideoCaptureMachine(aura::Window* window);
   ~DesktopVideoCaptureMachine() override;
 
   // VideoCaptureFrameSource overrides.
@@ -158,9 +158,6 @@ class DesktopVideoCaptureMachine
   // The timer that kicks off period captures.
   base::Timer timer_;
 
-  // The id of the window being captured.
-  DesktopMediaID window_id_;
-
   // Makes all the decisions about which frames to copy, and how.
   scoped_refptr<ThreadSafeCaptureOracle> oracle_proxy_;
 
@@ -182,11 +179,13 @@ class DesktopVideoCaptureMachine
   DISALLOW_COPY_AND_ASSIGN(DesktopVideoCaptureMachine);
 };
 
-DesktopVideoCaptureMachine::DesktopVideoCaptureMachine(
-    const DesktopMediaID& source)
-    : desktop_window_(NULL),
-      timer_(true, true),
-      window_id_(source) {}
+DesktopVideoCaptureMachine::DesktopVideoCaptureMachine(aura::Window* window)
+    : desktop_window_(window),
+      timer_(true, true) {
+  IncrementDesktopCaptureCounter(window->IsRootWindow()
+                                     ? SCREEN_CAPTURER_CREATED
+                                     : WINDOW_CAPTURER_CREATED);
+}
 
 DesktopVideoCaptureMachine::~DesktopVideoCaptureMachine() {}
 
@@ -195,10 +194,6 @@ bool DesktopVideoCaptureMachine::Start(
     const media::VideoCaptureParams& params) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  desktop_window_ = content::DesktopMediaID::GetAuraWindowById(window_id_);
-  if (!desktop_window_)
-    return false;
-
   // If the associated layer is already destroyed then return failure.
   ui::Layer* layer = desktop_window_->layer();
   if (!layer)
@@ -322,7 +317,7 @@ void DesktopVideoCaptureMachine::DidCopyOutput(
 
   // The two UMA_ blocks must be put in its own scope since it creates a static
   // variable which expected constant histogram name.
-  if (window_id_.type == DesktopMediaID::TYPE_SCREEN) {
+  if (desktop_window_->IsRootWindow()) {
     UMA_HISTOGRAM_TIMES(kUmaScreenCaptureTime, capture_time);
   } else {
     UMA_HISTOGRAM_TIMES(kUmaWindowCaptureTime, capture_time);
@@ -330,7 +325,7 @@ void DesktopVideoCaptureMachine::DidCopyOutput(
 
   if (first_call) {
     first_call = false;
-    if (window_id_.type == DesktopMediaID::TYPE_SCREEN) {
+    if (desktop_window_->IsRootWindow()) {
       IncrementDesktopCaptureCounter(succeeded ? FIRST_SCREEN_CAPTURE_SUCCEEDED
                                                : FIRST_SCREEN_CAPTURE_FAILED);
     } else {
@@ -510,10 +505,9 @@ void DesktopVideoCaptureMachine::OnCompositingEnded(
 
 }  // namespace
 
-DesktopCaptureDeviceAura::DesktopCaptureDeviceAura(
-    const DesktopMediaID& source)
+DesktopCaptureDeviceAura::DesktopCaptureDeviceAura(aura::Window* window)
     : core_(new ContentVideoCaptureDeviceCore(scoped_ptr<VideoCaptureMachine>(
-        new DesktopVideoCaptureMachine(source)))) {}
+        new DesktopVideoCaptureMachine(window)))) {}
 
 DesktopCaptureDeviceAura::~DesktopCaptureDeviceAura() {
   DVLOG(2) << "DesktopCaptureDeviceAura@" << this << " destroying.";
@@ -522,10 +516,8 @@ DesktopCaptureDeviceAura::~DesktopCaptureDeviceAura() {
 // static
 media::VideoCaptureDevice* DesktopCaptureDeviceAura::Create(
     const DesktopMediaID& source) {
-  IncrementDesktopCaptureCounter(source.type == DesktopMediaID::TYPE_SCREEN
-                                     ? SCREEN_CAPTURER_CREATED
-                                     : WINDOW_CAPTURER_CREATED);
-  return new DesktopCaptureDeviceAura(source);
+  aura::Window* window = content::DesktopMediaID::GetAuraWindowById(source);

[Sergey Ulanov, 2015/03/02 21:58:58]

DesktopMediaID::GetAuraWindowById() is not thread-safe and must be called on the
UI thread, while this code is executed on the device thread. Another related
problem is that |window| may be destroyed between Create() and
DesktopVideoCaptureMachine::Start() (note that Start() adds observer for the
window to get notified when it's destroyed). Sorry, I forgot about it when
reviewing your CL for virtual screens.

I suggest adding SetWindow(window) method in DesktopVideoCaptureMachine and
removing the window parameter from the constructor. Then you can post a task
from DesktopCaptureDeviceAura() to get window ID resolved on the UI thread.
After that, to get virtual screen implemented:
 1. Move DesktopVideoCaptureMachine to a separate file, and maybe rename it to
AuraWindowCaptureMachine.
 2. Add VirtualScreenCaptureDevice class that is the same
DesktopCaptureDeviceAura except it creates a virtual screen.

+  return new DesktopCaptureDeviceAura(window);
 }
 
 void DesktopCaptureDeviceAura::AllocateAndStart(