Set correct priorities on tasks and threads

Change-Id: I1dc8b466d0b45f9e1d6c973f1ad3c62033bf4409
Reviewed-by: Jüri Valdmann <juri.valdmann@qt.io>

src/core/compositor/compositor.cpp

@@ -56,7 +56,7 @@ Compositor::Compositor(content::RenderWidgetHost *host)
 {
     DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
 
-    m_taskRunner = base::CreateSingleThreadTaskRunnerWithTraits({content::BrowserThread::UI});
+    m_taskRunner = base::CreateSingleThreadTaskRunnerWithTraits({content::BrowserThread::UI, base::TaskPriority::USER_VISIBLE});
     m_beginFrameSource =
         std::make_unique<viz::DelayBasedBeginFrameSource>(
             std::make_unique<viz::DelayBasedTimeSource>(m_taskRunner.get()),

src/core/compositor/compositor_resource_tracker.cpp

@@ -244,7 +244,7 @@ void CompositorResourceTracker::updateMailboxes(std::vector<CompositorResource *
 void CompositorResourceTracker::scheduleRunSubmitCallback()
 {
     base::PostTaskWithTraits(
-        FROM_HERE, { content::BrowserThread::UI },
+        FROM_HERE, { content::BrowserThread::UI, base::TaskPriority::USER_VISIBLE },
         base::BindOnce(&CompositorResourceTracker::runSubmitCallback,
                        m_weakPtrFactory.GetWeakPtr()));
 }

src/core/web_engine_context_threads.cpp

@@ -82,7 +82,7 @@ struct GpuThreadControllerQt : content::GpuThreadController
         if (s_gpuProcessDestroyed)
             return;
 
-        s_gpuProcess = std::make_unique<content::GpuProcess>(base::ThreadPriority::NORMAL);
+        s_gpuProcess = std::make_unique<content::GpuProcess>(base::ThreadPriority::DISPLAY);
         auto gpuInit = std::make_unique<gpu::GpuInit>();
         gpuInit->InitializeInProcess(base::CommandLine::ForCurrentProcess(), gpuPreferences);
         auto childThread = new content::GpuChildThread(params, std::move(gpuInit));