Revert of Fix screen capturers to initialize on the same thread on which Start() is called.

webrtc/modules/desktop_capture/screen_capturer_mac.mm

Index: webrtc/modules/desktop_capture/screen_capturer_mac.mm
diff --git a/webrtc/modules/desktop_capture/screen_capturer_mac.mm b/webrtc/modules/desktop_capture/screen_capturer_mac.mm
index 2c22ee5e46fb43745fdd175d97330fbe2133f9fe..c41dc4d7a3b4ba59e4ebe6880f1e090dae5386b5 100644
--- a/webrtc/modules/desktop_capture/screen_capturer_mac.mm
+++ b/webrtc/modules/desktop_capture/screen_capturer_mac.mm
@@ -22,9 +22,7 @@
 #include <OpenGL/CGLMacro.h>
 #include <OpenGL/OpenGL.h>
 
-#include "webrtc/base/checks.h"
 #include "webrtc/base/macutils.h"
-#include "webrtc/base/thread_checker.h"
 #include "webrtc/modules/desktop_capture/desktop_capture_options.h"
 #include "webrtc/modules/desktop_capture/desktop_frame.h"
 #include "webrtc/modules/desktop_capture/desktop_geometry.h"
@@ -190,6 +188,8 @@
       rtc::scoped_refptr<DesktopConfigurationMonitor> desktop_config_monitor);
   virtual ~ScreenCapturerMac();
 
+  bool Init();
+
   // Overridden from ScreenCapturer:
   void Start(Callback* callback) override;
   void Capture(const DesktopRegion& region) override;
@@ -198,8 +198,6 @@
   bool SelectScreen(ScreenId id) override;
 
  private:
-  bool Initialize();
-
   void GlBlitFast(const DesktopFrame& frame,
                   const DesktopRegion& region);
   void GlBlitSlow(const DesktopFrame& frame);
@@ -230,11 +228,9 @@
 
   DesktopFrame* CreateFrame();
 
-  rtc::ThreadChecker thread_checker_;
-
-  Callback* callback_ = nullptr;
-
-  CGLContextObj cgl_context_ = nullptr;
+  Callback* callback_;
+
+  CGLContextObj cgl_context_;
   ScopedPixelBufferObject pixel_buffer_object_;
 
   // Queue of the frames buffers.
@@ -245,13 +241,13 @@
 
   // Currently selected display, or 0 if the full desktop is selected. On OS X
   // 10.6 and before, this is always 0.
-  CGDirectDisplayID current_display_ = 0;
+  CGDirectDisplayID current_display_;
 
   // The physical pixel bounds of the current screen.
   DesktopRect screen_pixel_bounds_;
 
   // The dip to physical pixel scale of the current screen.
-  float dip_to_pixel_scale_ = 1.0f;
+  float dip_to_pixel_scale_;
 
   // A thread-safe list of invalid rectangles, and the size of the most
   // recently captured screen.
@@ -264,20 +260,20 @@
   rtc::scoped_refptr<DesktopConfigurationMonitor> desktop_config_monitor_;
 
   // Power management assertion to prevent the screen from sleeping.
-  IOPMAssertionID power_assertion_id_display_ = kIOPMNullAssertionID;
+  IOPMAssertionID power_assertion_id_display_;
 
   // Power management assertion to indicate that the user is active.
-  IOPMAssertionID power_assertion_id_user_ = kIOPMNullAssertionID;
+  IOPMAssertionID power_assertion_id_user_;
 
   // Dynamically link to deprecated APIs for Mac OS X 10.6 support.
-  void* app_services_library_ = nullptr;
-  CGDisplayBaseAddressFunc cg_display_base_address_ = nullptr;
-  CGDisplayBytesPerRowFunc cg_display_bytes_per_row_ = nullptr;
-  CGDisplayBitsPerPixelFunc cg_display_bits_per_pixel_ = nullptr;
-  void* opengl_library_ = nullptr;
-  CGLSetFullScreenFunc cgl_set_full_screen_ = nullptr;
-
-  CGWindowID excluded_window_ = 0;
+  void* app_services_library_;
+  CGDisplayBaseAddressFunc cg_display_base_address_;
+  CGDisplayBytesPerRowFunc cg_display_bytes_per_row_;
+  CGDisplayBitsPerPixelFunc cg_display_bits_per_pixel_;
+  void* opengl_library_;
+  CGLSetFullScreenFunc cgl_set_full_screen_;
+
+  CGWindowID excluded_window_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(ScreenCapturerMac);
 };
@@ -307,15 +303,23 @@
 
 ScreenCapturerMac::ScreenCapturerMac(
     rtc::scoped_refptr<DesktopConfigurationMonitor> desktop_config_monitor)
-    : desktop_config_monitor_(desktop_config_monitor) {
-  // ScreenCapturer can be used on a thread different from the thread on which
-  // it's created.
-  thread_checker_.DetachFromThread();
+    : callback_(NULL),
+      cgl_context_(NULL),
+      current_display_(0),
+      dip_to_pixel_scale_(1.0f),
+      desktop_config_monitor_(desktop_config_monitor),
+      power_assertion_id_display_(kIOPMNullAssertionID),
+      power_assertion_id_user_(kIOPMNullAssertionID),
+      app_services_library_(NULL),
+      cg_display_base_address_(NULL),
+      cg_display_bytes_per_row_(NULL),
+      cg_display_bits_per_pixel_(NULL),
+      opengl_library_(NULL),
+      cgl_set_full_screen_(NULL),
+      excluded_window_(0) {
 }
 
 ScreenCapturerMac::~ScreenCapturerMac() {
-  RTC_DCHECK(thread_checker_.CalledOnValidThread());
-
   if (power_assertion_id_display_ != kIOPMNullAssertionID) {
     IOPMAssertionRelease(power_assertion_id_display_);
     power_assertion_id_display_ = kIOPMNullAssertionID;
@@ -331,7 +335,7 @@
   dlclose(opengl_library_);
 }
 
-bool ScreenCapturerMac::Initialize() {
+bool ScreenCapturerMac::Init() {
   if (!RegisterRefreshAndMoveHandlers()) {
     return false;
   }
@@ -355,16 +359,10 @@
 }
 
 void ScreenCapturerMac::Start(Callback* callback) {
-  RTC_DCHECK(thread_checker_.CalledOnValidThread());
-  RTC_DCHECK(!callback_);
-  RTC_DCHECK(callback);
+  assert(!callback_);
+  assert(callback);
 
   callback_ = callback;
-
-  if (!Initialize()) {
-    callback_->OnInitializationFailed();
-    return;
-  }
 
   // Create power management assertions to wake the display and prevent it from
   // going to sleep on user idle.
@@ -383,8 +381,6 @@
 }
 
 void ScreenCapturerMac::Capture(const DesktopRegion& region_to_capture) {
-  RTC_DCHECK(thread_checker_.CalledOnValidThread());
-
   TickTime capture_start_time = TickTime::Now();
 
   queue_.MoveToNextFrame();
@@ -453,14 +449,11 @@
 }
 
 void ScreenCapturerMac::SetExcludedWindow(WindowId window) {
-  RTC_DCHECK(thread_checker_.CalledOnValidThread());
   excluded_window_ = window;
 }
 
 bool ScreenCapturerMac::GetScreenList(ScreenList* screens) {
-  RTC_DCHECK(thread_checker_.CalledOnValidThread());
-  RTC_DCHECK(screens->size() == 0);
-
+  assert(screens->size() == 0);
   if (rtc::GetOSVersionName() < rtc::kMacOSLion) {
     // Single monitor cast is not supported on pre OS X 10.7.
     Screen screen;
@@ -479,8 +472,6 @@
 }
 
 bool ScreenCapturerMac::SelectScreen(ScreenId id) {
-  RTC_DCHECK(thread_checker_.CalledOnValidThread());
-
   if (rtc::GetOSVersionName() < rtc::kMacOSLion) {
     // Ignore the screen selection on unsupported OS.
     assert(!current_display_);
@@ -989,7 +980,11 @@
   if (!options.configuration_monitor())
     return NULL;
 
-  return new ScreenCapturerMac(options.configuration_monitor());
+  std::unique_ptr<ScreenCapturerMac> capturer(
+      new ScreenCapturerMac(options.configuration_monitor()));
+  if (!capturer->Init())
+    capturer.reset();
+  return capturer.release();
 }
 
 }  // namespace webrtc