cc: Clean up RecordingSource API

cc/proto/recording_source.proto

Index: cc/proto/recording_source.proto
diff --git a/cc/proto/recording_source.proto b/cc/proto/recording_source.proto
index 519ccf03f5d1e4cc72daf192180ab52ae1a0826b..a4954f6cb567b024005f78c463d6add89ac5a0b8 100644
--- a/cc/proto/recording_source.proto
+++ b/cc/proto/recording_source.proto
@@ -4,8 +4,6 @@
 
 syntax = "proto2";
 
-import "display_item.proto";
-import "rect.proto";
 import "size.proto";
 
 option optimize_for = LITE_RUNTIME;
@@ -14,14 +12,12 @@ package cc.proto;
 
 // A serialized representation of the RecordingSource class.
 message RecordingSource {
-  optional Rect recorded_viewport = 1;
-  optional Size size = 2;
-  optional int64 slow_down_raster_scale_factor_for_debug = 3;
-  optional bool generate_discardable_images_metadata = 4;
-  optional bool requires_clear = 5;
-  optional bool is_solid_color = 6;
-  optional bool clear_canvas_with_debug_color = 7;
-  optional uint64 solid_color = 8;
-  optional uint64 background_color = 9;
-  optional DisplayItemList display_list = 10;
+  optional Size size = 1;
+  optional int64 slow_down_raster_scale_factor_for_debug = 2;
+  optional bool generate_discardable_images_metadata = 3;
+  optional bool requires_clear = 4;
+  optional bool is_solid_color = 5;
+  optional bool clear_canvas_with_debug_color = 6;
+  optional uint64 solid_color = 7;
+  optional uint64 background_color = 8;
 }