Disable rendering when suspending on chrome os

ash/system/chromeos/power/power_event_observer.cc

Index: ash/system/chromeos/power/power_event_observer.cc
diff --git a/ash/system/chromeos/power/power_event_observer.cc b/ash/system/chromeos/power/power_event_observer.cc
index 65567f4ed0212ae97e70810a73ca2cb144506225..78612d3d2084f5d60172f0892822c71b552490bd 100644
--- a/ash/system/chromeos/power/power_event_observer.cc
+++ b/ash/system/chromeos/power/power_event_observer.cc
@@ -8,9 +8,13 @@
 #include "ash/shell.h"
 #include "ash/system/tray/system_tray_notifier.h"
 #include "ash/wm/power_button_controller.h"
+#include "base/message_loop/message_loop.h"
 #include "base/prefs/pref_service.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
+#include "ui/aura/window.h"
+#include "ui/aura/window_tree_host.h"
 #include "ui/base/user_activity/user_activity_detector.h"
+#include "ui/compositor/compositor.h"
 #include "ui/display/chromeos/display_configurator.h"
 
 namespace ash {
@@ -48,6 +52,13 @@ void PowerEventObserver::SuspendImminent() {
     VLOG(1) << "Requesting screen lock from PowerEventObserver";
     chromeos::DBusThreadManager::Get()->GetSessionManagerClient()->
         RequestLockScreen();
+  } else {
+    // If the screen needs to be locked then rendering requests must be blocked
+    // _after_ the lock screen is visible.  Otherwise the display will show the
+    // contents of the user's screen at resume time, which is a security issue.
+    // This is handled in the ScreenIsLocked() method.  In case the screen does
+    // not need to be locked, we can stop rendering now.
+    StopRenderingRequests();
   }
 
   ui::UserActivityDetector::Get()->OnDisplayPowerChanging();
@@ -57,6 +68,13 @@ void PowerEventObserver::SuspendImminent() {
 void PowerEventObserver::SuspendDone(const base::TimeDelta& sleep_duration) {
   Shell::GetInstance()->display_configurator()->ResumeDisplays();
   Shell::GetInstance()->system_tray_notifier()->NotifyRefreshClock();
+
+  ResumeRenderingRequests();
+
+  // If the suspend request was being blocked, clear the callback since the
+  // request has already completed.  This prevents rendering requests from being
+  // blocked after a resume if the lock screen took too long to show.
+  screen_lock_callback_.Reset();
 }
 
 void PowerEventObserver::ScreenIsLocked() {
@@ -65,6 +83,10 @@ void PowerEventObserver::ScreenIsLocked() {
   // Stop blocking suspend after the screen is locked.
   if (!screen_lock_callback_.is_null()) {
     VLOG(1) << "Screen locked due to suspend";
+
+    // Stop the compositors from making any new rendering requests.
+    StopRenderingRequests();
+
     // Run the callback asynchronously.  ScreenIsLocked() is currently
     // called asynchronously after RequestLockScreen(), but this guards
     // against it being made synchronous later.
@@ -79,4 +101,20 @@ void PowerEventObserver::ScreenIsUnlocked() {
   screen_locked_ = false;
 }
 
+void PowerEventObserver::ResumeRenderingRequests() {
+  for (aura::Window* window : Shell::GetAllRootWindows()) {
+    ui::Compositor* compositor = window->GetHost()->compositor();
+    compositor->SetVisible(true);
+    compositor->ScheduleDraw();

[piman, 2015/02/11 02:48:22]

I don't think the ScheduleDraw should be needed.

[Chirantan Ekbote, 2015/02/18 02:47:13]

Done.

+  }
+}
+
+void PowerEventObserver::StopRenderingRequests() {
+  for (aura::Window* window : Shell::GetAllRootWindows()) {
+    ui::Compositor* compositor = window->GetHost()->compositor();
+    compositor->SetVisible(false);
+    compositor->DisableSwap();
+  }
+}
+
 }  // namespace ash