Bug 1600032: Make GPUVideoTextureHost plugin lookup infallible r=mattwoodrow

If the D3D11TextureData backing the plugin variant of a GPUVideoTextureHost is requested, but the ImageBridge has already released or lost it then, instead of null, we now return a NullPluginTextureHost in order to avoid IPDL serialization failure down the line.  This mirrors the degenerate case of RemoteVideoDecoder behavior, indroduced to fix the same issue with that variant of GPUVideoTextureHost, in bug 1562616.

Differential Revision: https://phabricator.services.mozilla.com/D55843

--HG--
extra : moz-landing-system : lando

gfx/layers/ipc/ImageBridgeParent.cpp

@@ -641,12 +641,69 @@ mozilla::ipc::IPCResult ImageBridgeParent::RecvRemoveAsyncPluginSurface(
   return IPC_OK();
 }
 
+#if defined(OS_WIN)
+RefPtr<TextureHost> GetNullPluginTextureHost() {
+  class NullPluginTextureHost : public TextureHost {
+   public:
+    NullPluginTextureHost() : TextureHost(TextureFlags::NO_FLAGS) {}
+
+    ~NullPluginTextureHost() {}
+
+    gfx::SurfaceFormat GetFormat() const override {
+      return gfx::SurfaceFormat::UNKNOWN;
+    }
+
+    already_AddRefed<gfx::DataSourceSurface> GetAsSurface() override {
+      return nullptr;
+    }
+
+    gfx::IntSize GetSize() const override { return gfx::IntSize(); }
+
+    bool BindTextureSource(CompositableTextureSourceRef& aTexture) override {
+      return false;
+    }
+
+    const char* Name() override { return "NullPluginTextureHost"; }
+
+    virtual bool Lock() { return false; }
+
+    void CreateRenderTexture(
+        const wr::ExternalImageId& aExternalImageId) override {}
+
+    uint32_t NumSubTextures() override { return 0; }
+
+    void PushResourceUpdates(wr::TransactionBuilder& aResources,
+                             ResourceUpdateOp aOp,
+                             const Range<wr::ImageKey>& aImageKeys,
+                             const wr::ExternalImageId& aExtID,
+                             const bool aPreferCompositorSurface) override {}
+
+    void PushDisplayItems(wr::DisplayListBuilder& aBuilder,
+                          const wr::LayoutRect& aBounds,
+                          const wr::LayoutRect& aClip,
+                          wr::ImageRendering aFilter,
+                          const Range<wr::ImageKey>& aImageKeys) override {}
+  };
+
+  static StaticRefPtr<TextureHost> sNullPluginTextureHost;
+  if (!sNullPluginTextureHost) {
+    sNullPluginTextureHost = new NullPluginTextureHost();
+    ClearOnShutdown(&sNullPluginTextureHost);
+  };
+
+  MOZ_ASSERT(sNullPluginTextureHost);
+  return sNullPluginTextureHost.get();
+}
+#endif  // defined(OS_WIN)
+
 RefPtr<TextureHost> ImageBridgeParent::LookupTextureHost(
     const SurfaceDescriptorPlugin& aDescriptor) {
 #if defined(OS_WIN)
   auto it = mGPUVideoTextureHosts.lookup(aDescriptor.id());
-  return it ? it->value() : nullptr;
+  RefPtr<TextureHost> ret = it ? it->value() : nullptr;
+  return ret ? ret : GetNullPluginTextureHost();
 #else
+  MOZ_ASSERT_UNREACHABLE("Unsupported architecture.");
   return nullptr;
 #endif  // defined(OS_WIN)
 }