Don't update framebuffer_size to 0x0 when the framebuffer size didn't change.

ui/display/chromeos/display_configurator.cc

Index: ui/display/chromeos/display_configurator.cc
diff --git a/ui/display/chromeos/display_configurator.cc b/ui/display/chromeos/display_configurator.cc
index 5e8bccf328b514c3a29b1c3e653e46b23cf2cf02..9ead66156fb6165fb2f20262f31107dee10cedd6 100644
--- a/ui/display/chromeos/display_configurator.cc
+++ b/ui/display/chromeos/display_configurator.cc
@@ -323,7 +323,8 @@ bool DisplayConfigurator::DisplayLayoutManagerImpl::GetDisplayLayout(
       break;
     }
   }
-
+  DCHECK(new_display_state == MULTIPLE_DISPLAY_STATE_HEADLESS ||
+         !size.IsEmpty());
   *framebuffer_size = size;
   return true;
 }
@@ -919,7 +920,17 @@ void DisplayConfigurator::OnConfigured(
   if (success) {
     current_display_state_ = new_display_state;
     current_power_state_ = new_power_state;
-    framebuffer_size_ = framebuffer_size;
+
+    // |framebuffer_size| is empty in software mirroring mode, headless mode,
+    // or all displays are off.
+    DCHECK(!framebuffer_size.IsEmpty() ||
+           mirroring_controller_->SoftwareMirroringEnabled() ||
+           new_display_state == MULTIPLE_DISPLAY_STATE_HEADLESS ||
+           new_power_state == chromeos::DISPLAY_POWER_ALL_OFF);

[dnicoara, 2015/03/20 18:36:42]

Shouldn't happen when the display power is all off.
DisplayLayoutManagerImpl::GetDisplayLayout will compute the framebuffer size
based on the selected mode, disregarding the requested power state.

[oshima, 2015/03/20 20:30:08]

when suspending display(s), it may skip actual configuration, which leads to
this state. 

[dnicoara, 2015/03/20 20:37:36]

Acknowledged.

+
+    if (!framebuffer_size.IsEmpty())
+      framebuffer_size_ = framebuffer_size;
+
     // If the requested power state hasn't changed then make sure that value
     // gets updated as well since the last requested value may have been
     // dependent on certain conditions (ie: if only the internal monitor was