cc/blimp: Set up the framework for state serialization.

cc/blimp/compositor_proto_state.h

Index: cc/blimp/compositor_proto_state.h
diff --git a/cc/blimp/compositor_proto_state.h b/cc/blimp/compositor_proto_state.h
index 536cb6858e8630cc1635522a63035af703191518..81c3b019e839b7d8f05b8d977a1133705b5db133 100644
--- a/cc/blimp/compositor_proto_state.h
+++ b/cc/blimp/compositor_proto_state.h
@@ -5,12 +5,17 @@
 #ifndef CC_BLIMP_COMPOSITOR_PROTO_STATE_H_
 #define CC_BLIMP_COMPOSITOR_PROTO_STATE_H_
 
+#include <memory>
 #include <vector>
 
 #include "base/macros.h"
 #include "cc/base/cc_export.h"
 
 namespace cc {
+namespace proto {
+class CompositorMessage;
+}
+
 class SwapPromise;
 
 class CC_EXPORT CompositorProtoState {
@@ -19,10 +24,10 @@ class CC_EXPORT CompositorProtoState {
   ~CompositorProtoState();
 
   // The SwapPromises associated with this frame update.
-  std::vector<SwapPromise> swap_promises;
+  std::vector<std::unique_ptr<SwapPromise>> swap_promises;
 
-  // TODO(khushalsagar): Add serialized representation of the layers, layer tree
-  // and display lists.
+  // Serialized CompositorState.
+  std::unique_ptr<proto::CompositorMessage> compositor_message;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(CompositorProtoState);