Bug 1436020 - Disable WebRender profiler UI during readback r=nical

gfx/webrender_bindings/RenderThread.cpp

@@ -239,7 +239,7 @@ NotifyDidRender(layers::CompositorBridgeParentBase* aBridge,
 }
 
 void
-RenderThread::UpdateAndRender(wr::WindowId aWindowId)
+RenderThread::UpdateAndRender(wr::WindowId aWindowId, bool aReadback)
 {
   AUTO_PROFILER_TRACING("Paint", "Composite");
   MOZ_ASSERT(IsInRenderThread());
@@ -253,7 +253,7 @@ RenderThread::UpdateAndRender(wr::WindowId aWindowId)
   auto& renderer = it->second;
   TimeStamp start = TimeStamp::Now();
 
-  bool ret = renderer->UpdateAndRender();
+  bool ret = renderer->UpdateAndRender(aReadback);
   if (!ret) {
     // Render did not happen, do not call NotifyDidRender.
     return;

gfx/webrender_bindings/RenderThread.h

@@ -127,7 +127,7 @@ public:
   void RunEvent(wr::WindowId aWindowId, UniquePtr<RendererEvent> aCallBack);
 
   /// Can only be called from the render thread.
-  void UpdateAndRender(wr::WindowId aWindowId);
+  void UpdateAndRender(wr::WindowId aWindowId, bool aReadback = false);
 
   void Pause(wr::WindowId aWindowId);
   bool Resume(wr::WindowId aWindowId);

gfx/webrender_bindings/RendererOGL.cpp

@@ -88,9 +88,13 @@ RendererOGL::Update()
 }
 
 bool
-RendererOGL::UpdateAndRender()
+RendererOGL::UpdateAndRender(bool aReadback)
 {
   uint32_t flags = gfx::gfxVars::WebRenderDebugFlags();
+  // Disable debug flags during readback
+  if (aReadback) {
+    flags = 0;
+  }
 
   if (mDebugFlags.mBits != flags) {
     mDebugFlags.mBits = flags;

gfx/webrender_bindings/RendererOGL.h

@@ -53,7 +53,7 @@ public:
   void Update();
 
   /// This can be called on the render thread only.
-  bool UpdateAndRender();
+  bool UpdateAndRender(bool aReadback);
 
   /// This can be called on the render thread only.
   bool RenderToTarget(gfx::DrawTarget& aTarget);

gfx/webrender_bindings/WebRenderAPI.cpp

@@ -400,7 +400,7 @@ WebRenderAPI::Readback(gfx::IntSize size,
 
             virtual void Run(RenderThread& aRenderThread, WindowId aWindowId) override
             {
-                aRenderThread.UpdateAndRender(aWindowId);
+                aRenderThread.UpdateAndRender(aWindowId, /* aReadback */ true);
                 wr_renderer_readback(aRenderThread.GetRenderer(aWindowId)->GetRenderer(),
                                      mSize.width, mSize.height, mBuffer, mBufferSize);
                 layers::AutoCompleteTask complete(mTask);