[blimp] Add support for having multiple tabs

blimp/client/core/compositor/blimp_compositor_manager.h

Index: blimp/client/core/compositor/blimp_compositor_manager.h
diff --git a/blimp/client/core/compositor/blimp_compositor_manager.h b/blimp/client/core/compositor/blimp_compositor_manager.h
index dc1dfbd13a63e4b235235aff324961e661a0f0e1..2d12e0ee5ba0ec1ac1b6504e83229761253faa5c 100644
--- a/blimp/client/core/compositor/blimp_compositor_manager.h
+++ b/blimp/client/core/compositor/blimp_compositor_manager.h
@@ -28,6 +28,7 @@ class BlimpCompositorManager
       public BlimpCompositorClient {
  public:
   explicit BlimpCompositorManager(
+      int blimp_contents_id,
       RenderWidgetFeature* render_widget_feature,
       BlimpCompositorDependencies* compositor_dependencies);
   ~BlimpCompositorManager() override;
@@ -67,6 +68,8 @@ class BlimpCompositorManager
       int render_widget_id,
       const cc::proto::CompositorMessage& message) override;
 
+  int blimp_contents_id_;
+
   // The bridge to the network layer that does the proto/RenderWidget id work.
   // BlimpCompositorManager does not own this and it is expected to outlive this
   // BlimpCompositorManager instance.