--- a/gfx/layers/wr/WebRenderLayerManager.cpp
+++ b/gfx/layers/wr/WebRenderLayerManager.cpp
@@ -17,16 +17,20 @@
 #include "mozilla/layers/IpcResourceUpdateQueue.h"
 #include "mozilla/layers/StackingContextHelper.h"
 #include "mozilla/layers/TextureClient.h"
 #include "mozilla/layers/WebRenderBridgeChild.h"
 #include "mozilla/layers/UpdateImageHelper.h"
 #include "nsDisplayList.h"
 #include "WebRenderCanvasRenderer.h"
 
+// Useful for debugging, it dumps the Gecko display list *before* we try to
+// build WR commands from it, and dumps the WR display list after building it.
+#define DUMP_LISTS 0
+
 namespace mozilla {
 
 using namespace gfx;
 
 namespace layers {
 
 WebRenderLayerManager::WebRenderLayerManager(nsIWidget* aWidget)
   : mWidget(aWidget)
@@ -243,20 +247,20 @@ void
 WebRenderLayerManager::EndTransactionWithoutLayer(nsDisplayList* aDisplayList,
                                                   nsDisplayListBuilder* aDisplayListBuilder)
 {
   MOZ_ASSERT(aDisplayList && aDisplayListBuilder);
   WrBridge()->RemoveExpiredFontKeys();
 
   AUTO_PROFILER_TRACING("Paint", "RenderLayers");
 
-#if 0
+#if DUMP_LISTS
   // Useful for debugging, it dumps the display list *before* we try to build
   // WR commands from it
-  nsFrame::PrintDisplayList(aDisplayListBuilder, *aDisplayList);
+  if (XRE_IsContentProcess()) nsFrame::PrintDisplayList(aDisplayListBuilder, *aDisplayList);
 #endif
 
   // Since we don't do repeat transactions right now, just set the time
   mAnimationReadyTime = TimeStamp::Now();
 
   WrBridge()->BeginTransaction();
   DiscardCompositorAnimations();
 
@@ -301,16 +305,20 @@ WebRenderLayerManager::EndTransactionWit
   // device-reset status.
   if (!gfxPlatform::GetPlatform()->DidRenderingDeviceReset()) {
     if (WrBridge()->GetSyncObject() &&
         WrBridge()->GetSyncObject()->IsSyncObjectValid()) {
       WrBridge()->GetSyncObject()->Synchronize();
     }
   }
 
+#if DUMP_LISTS
+  if (XRE_IsContentProcess()) builder.Dump();
+#endif
+
   wr::BuiltDisplayList dl;
   builder.Finalize(contentSize, dl);
   mLastDisplayListSize = dl.dl.inner.capacity;
 
   {
     AUTO_PROFILER_TRACING("Paint", "ForwardDPTransaction");
     WrBridge()->EndTransaction(contentSize, dl, resourceUpdates, size.ToUnknownSize(),
                                mLatestTransactionId, mScrollData, transactionStart);

--- a/gfx/webrender_bindings/WebRenderAPI.cpp
+++ b/gfx/webrender_bindings/WebRenderAPI.cpp
@@ -685,16 +685,17 @@ DisplayListBuilder::~DisplayListBuilder(
 {
   MOZ_COUNT_DTOR(DisplayListBuilder);
   wr_state_delete(mWrState);
 }
 
 void DisplayListBuilder::Save() { wr_dp_save(mWrState); }
 void DisplayListBuilder::Restore() { wr_dp_restore(mWrState); }
 void DisplayListBuilder::ClearSave() { wr_dp_clear_save(mWrState); }
+void DisplayListBuilder::Dump() { wr_dump_display_list(mWrState); }
 
 void
 DisplayListBuilder::Finalize(wr::LayoutSize& aOutContentSize,
                              BuiltDisplayList& aOutDisplayList)
 {
   wr_api_finalize_builder(mWrState,
                           &aOutContentSize,
                           &aOutDisplayList.dl_desc,

--- a/gfx/webrender_bindings/WebRenderAPI.h
+++ b/gfx/webrender_bindings/WebRenderAPI.h
@@ -223,16 +223,17 @@ public:
                               size_t aCapacity = 0);
   DisplayListBuilder(DisplayListBuilder&&) = default;
 
   ~DisplayListBuilder();
 
   void Save();
   void Restore();
   void ClearSave();
+  void Dump();
 
   void Finalize(wr::LayoutSize& aOutContentSize,
                 wr::BuiltDisplayList& aOutDisplayList);
 
   void PushStackingContext(const wr::LayoutRect& aBounds, // TODO: We should work with strongly typed rects
                            const wr::WrAnimationProperty* aAnimation,
                            const float* aOpacity,
                            const gfx::Matrix4x4* aTransform,

--- a/gfx/webrender_bindings/src/bindings.rs
+++ b/gfx/webrender_bindings/src/bindings.rs
@@ -1933,16 +1933,23 @@ pub extern "C" fn wr_dp_push_box_shadow(
                           color,
                           blur_radius,
                           spread_radius,
                           border_radius,
                           clip_mode);
 }
 
 #[no_mangle]
+pub extern "C" fn wr_dump_display_list(state: &mut WrState) {
+    state.frame_builder
+         .dl_builder
+         .print_display_list();
+}
+
+#[no_mangle]
 pub unsafe extern "C" fn wr_api_finalize_builder(state: &mut WrState,
                                                  content_size: &mut LayoutSize,
                                                  dl_descriptor: &mut BuiltDisplayListDescriptor,
                                                  dl_data: &mut WrVecU8) {
     let frame_builder = mem::replace(&mut state.frame_builder,
                                      WebRenderFrameBuilder::new(state.pipeline_id,
                                                                 LayoutSize::zero()));
     let (_, size, dl) = frame_builder.dl_builder.finalize();

--- a/gfx/webrender_bindings/webrender_ffi_generated.h
+++ b/gfx/webrender_bindings/webrender_ffi_generated.h
@@ -1387,16 +1387,20 @@ WR_INLINE
 void wr_dp_restore(WrState *aState)
 WR_FUNC;
 
 WR_INLINE
 void wr_dp_save(WrState *aState)
 WR_FUNC;
 
 WR_INLINE
+void wr_dump_display_list(WrState *aState)
+WR_FUNC;
+
+WR_INLINE
 void wr_init_external_log_handler(WrLogLevelFilter aLogFilter)
 WR_FUNC;
 
 extern bool wr_moz2d_render_cb(ByteSlice aBlob,
                                uint32_t aWidth,
                                uint32_t aHeight,
                                ImageFormat aFormat,
                                const uint16_t *aTileSize,