Bug 1417519 - Don't allow things to get raw pointers to WebRenderAPI. r=sotaro

It seems like a footgun to expose raw pointers to WebRenderAPI which is
a refcounted object. Let's only expose it via refcounting pointers.

MozReview-Commit-ID: AKmTZg2V99r

--HG--
extra : rebase_source : 805f13d56a64bafbcdf3bf4266eec47c70856564

gfx/layers/ipc/CompositorBridgeParent.cpp

@@ -1659,7 +1659,8 @@ CompositorBridgeParent::RecvAdoptChild(const uint64_t& child)
       ScheduleComposition();
     }
     if (mWrBridge && sIndirectLayerTrees[child].mWrBridge) {
-      RefPtr<wr::WebRenderAPI> api = mWrBridge->GetWebRenderAPI()->Clone();
+      RefPtr<wr::WebRenderAPI> api = mWrBridge->GetWebRenderAPI();
+      api = api->Clone();
       sIndirectLayerTrees[child].mWrBridge->UpdateWebRender(mWrBridge->CompositorScheduler(),
                                                             api,
                                                             mWrBridge->AsyncImageManager(),

gfx/layers/ipc/CrossProcessCompositorBridgeParent.cpp

@@ -228,7 +228,8 @@ CrossProcessCompositorBridgeParent::AllocPWebRenderBridgeParent(const wr::Pipeli
     return parent;
   }
 
-  RefPtr<wr::WebRenderAPI> api = root->GetWebRenderAPI()->Clone();
+  RefPtr<wr::WebRenderAPI> api = root->GetWebRenderAPI();
+  api = api->Clone();
   RefPtr<AsyncImagePipelineManager> holder = root->AsyncImageManager();
   RefPtr<CompositorAnimationStorage> animStorage = cbp->GetAnimationStorage();
   parent = new WebRenderBridgeParent(this, aPipelineId, nullptr, root->CompositorScheduler(), Move(api), Move(holder), Move(animStorage));

gfx/layers/wr/WebRenderBridgeParent.h

@@ -58,7 +58,7 @@ public:
   static WebRenderBridgeParent* CreateDestroyed(const wr::PipelineId& aPipelineId);
 
   wr::PipelineId PipelineId() { return mPipelineId; }
-  wr::WebRenderAPI* GetWebRenderAPI() { return mApi; }
+  already_AddRefed<wr::WebRenderAPI> GetWebRenderAPI() { return do_AddRef(mApi); }
   wr::Epoch WrEpoch() { return wr::NewEpoch(mWrEpoch); }
   AsyncImagePipelineManager* AsyncImageManager() { return mAsyncImageManager; }
   CompositorVsyncScheduler* CompositorScheduler() { return mCompositorScheduler.get(); }