Re-upload - Fix crash when we don't have a plane to display

Review URL: https://codereview.chromium.org/794323006

Cr-Commit-Position: refs/heads/master@{#308364}

ui/ozone/platform/dri/crtc_controller.cc

@@ -63,13 +63,17 @@ bool CrtcController::SchedulePageFlip(HardwareDisplayPlaneList* plane_list,
                                       const OverlayPlaneList& overlays) {
   DCHECK(!page_flip_pending_);
   DCHECK(!is_disabled_);
-  const OverlayPlane& primary = OverlayPlane::GetPrimaryPlane(overlays);
-  DCHECK(primary.buffer.get());
+  const OverlayPlane* primary = OverlayPlane::GetPrimaryPlane(overlays);
+  if (!primary) {
+    LOG(ERROR) << "No primary plane to display on crtc " << crtc_;
+    return true;
+  }
+  DCHECK(primary->buffer.get());
 
-  if (primary.buffer->GetSize() != gfx::Size(mode_.hdisplay, mode_.vdisplay)) {
+  if (primary->buffer->GetSize() != gfx::Size(mode_.hdisplay, mode_.vdisplay)) {
     LOG(WARNING) << "Trying to pageflip a buffer with the wrong size. Expected "
                  << mode_.hdisplay << "x" << mode_.vdisplay << " got "
-                 << primary.buffer->GetSize().ToString() << " for"
+                 << primary->buffer->GetSize().ToString() << " for"
                  << " crtc=" << crtc_ << " connector=" << connector_;
     return true;
   }

ui/ozone/platform/dri/hardware_display_controller.cc

@@ -74,11 +74,11 @@ bool HardwareDisplayController::Modeset(const OverlayPlane& primary,
 bool HardwareDisplayController::Enable() {
   TRACE_EVENT0("dri", "HDC::Enable");
   DCHECK(!current_planes_.empty());
-  OverlayPlane primary = OverlayPlane::GetPrimaryPlane(current_planes_);
-  DCHECK(primary.buffer.get());
+  const OverlayPlane* primary = OverlayPlane::GetPrimaryPlane(current_planes_);
+  DCHECK(primary->buffer.get());
   bool status = true;
   for (size_t i = 0; i < crtc_controllers_.size(); ++i)
-    status &= crtc_controllers_[i]->Modeset(primary, mode_);
+    status &= crtc_controllers_[i]->Modeset(*primary, mode_);
 
   return status;
 }

ui/ozone/platform/dri/overlay_plane.cc

@@ -32,15 +32,14 @@ OverlayPlane::~OverlayPlane() {
 }
 
 // static
-const OverlayPlane& OverlayPlane::GetPrimaryPlane(
+const OverlayPlane* OverlayPlane::GetPrimaryPlane(
     const OverlayPlaneList& overlays) {
   for (size_t i = 0; i < overlays.size(); ++i) {
     if (overlays[i].z_order == 0)
-      return overlays[i];
+      return &overlays[i];
   }
 
-  NOTREACHED();
-  return overlays[0];
+  return nullptr;
 }
 
 }  // namespace ui

ui/ozone/platform/dri/overlay_plane.h

@@ -31,7 +31,7 @@ struct OverlayPlane {
   ~OverlayPlane();
 
   // Returns the primary plane in |overlays|.
-  static const OverlayPlane& GetPrimaryPlane(const OverlayPlaneList& overlays);
+  static const OverlayPlane* GetPrimaryPlane(const OverlayPlaneList& overlays);
 
   scoped_refptr<ScanoutBuffer> buffer;
   int z_order;