cc/blimp: Add synchronization for scroll/scale state.

cc/proto/client_state_update.proto

Index: cc/proto/client_state_update.proto
diff --git a/cc/proto/commit_earlyout_reason.proto b/cc/proto/client_state_update.proto
similarity index 51%
copy from cc/proto/commit_earlyout_reason.proto
copy to cc/proto/client_state_update.proto
index 092fbd34b437276056e0b42fbb560bb3f57c74ea..38d7074c54420f4f9f14ca6f308b354f1a52a705 100644
--- a/cc/proto/commit_earlyout_reason.proto
+++ b/cc/proto/client_state_update.proto
@@ -6,15 +6,16 @@ syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
-package cc.proto;
+import "vector2d.proto";
 
-message CommitEarlyOutReason {
-  enum Reason {
-    ABORTED_COMPOSITOR_FRAME_SINK_LOST = 1;
-    ABORTED_NOT_VISIBLE = 2;
-    ABORTED_DEFERRED_COMMIT = 3;
-    FINISHED_NO_UPDATES = 4;
-  }
+package cc.proto;
 
-  optional Reason reason = 1;
+message ScrollUpdate {
+  optional int32 layer_id = 1;
+  optional Vector2d scroll_delta = 2;
 }
+
+message ClientStateUpdate {
+  repeated ScrollUpdate scroll_updates = 1;
+  optional float page_scale_delta = 2;
+}