Fix use_image_texture_target inconsistencies

cc/proto/renderer_settings.proto

Index: cc/proto/renderer_settings.proto
diff --git a/cc/proto/renderer_settings.proto b/cc/proto/renderer_settings.proto
index 55e692ec92d49572e77e52729ca442ff3f43835f..638816433e4258104b8322fa712abb1be9fc0041 100644
--- a/cc/proto/renderer_settings.proto
+++ b/cc/proto/renderer_settings.proto
@@ -8,6 +8,12 @@ package cc.proto;
 
 option optimize_for = LITE_RUNTIME;
 
+message UseImageTextureTargets {
+  optional uint32 buffer_usage = 1;

[erikchen, 2016/07/15 21:08:35]

should these be required?

[ericrk, 2016/07/19 20:22:43]

Although these are "required", we use optional for all fields, as using required
makes deprecating fields much harder.

+  optional uint32 buffer_format = 2;
+  optional uint32 texture_target = 3;
+};
+
 message RendererSettings {
   optional bool allow_antialiasing = 1;
   optional bool force_antialiasing = 2;
@@ -22,4 +28,5 @@ message RendererSettings {
   optional uint32 texture_id_allocation_chunk_size = 11;
   optional bool use_gpu_memory_buffer_resources = 12;
   optional uint32 preferred_tile_format = 13;
+  repeated UseImageTextureTargets use_image_texture_targets = 14;
 }