Bug 1494528 - Call GPUProcessManager::EnsureGPUReady() before accessing gfxVars::UseWebRender() r=aosmond

widget/nsBaseWidget.cpp

@@ -1313,6 +1313,12 @@ nsBaseWidget::CreateCompositorSession(int aWidth,
   do {
     CreateCompositorVsyncDispatcher();
 
+    gfx::GPUProcessManager* gpu = gfx::GPUProcessManager::Get();
+    // Make sure GPU process is ready for use.
+    // If it failed to connect to GPU process, GPU process usage is disabled in EnsureGPUReady().
+    // It could update gfxVars and gfxConfigs.
+    gpu->EnsureGPUReady();
+
     // If widget type does not supports acceleration, we use ClientLayerManager
     // even when gfxVars::UseWebRender() is true. WebRender could coexist only
     // with BasicCompositor.
@@ -1338,7 +1344,6 @@ nsBaseWidget::CreateCompositorSession(int aWidth,
     }
 
     bool retry = false;
-    gfx::GPUProcessManager* gpu = gfx::GPUProcessManager::Get();
     mCompositorSession = gpu->CreateTopLevelCompositor(
       this,
       lm,