Copy NV12 picture buffers on demand on the main thread.

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 49f4fc74411d1b356bb200102ce74d7f6bac8861..2d8cfa0898d25b55432d11520c13022691bb46d6 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -9668,7 +9668,11 @@ void GLES2DecoderImpl::DoCopyTexImageIfNeeded(Texture* texture,
       ScopedGLErrorSuppressor suppressor(
           "GLES2DecoderImpl::DoCopyTexImageIfNeeded", GetErrorState());
       glBindTexture(textarget, texture->service_id());
-      DoCopyTexImage(texture, textarget, image);
+      if (image->BindTexImage(textarget)) {
+        image_state = Texture::BOUND;
+      } else {
+        DoCopyTexImage(texture, textarget, image);
+      }
       RestoreCurrentTextureBindings(&state_, textarget);
     }
   }
@@ -9733,9 +9737,13 @@ bool GLES2DecoderImpl::PrepareTexturesForRender() {
               !texture->IsAttachedToFramebuffer()) {
             ScopedGLErrorSuppressor suppressor(
                 "GLES2DecoderImpl::PrepareTexturesForRender", GetErrorState());
-            textures_set = true;
             glActiveTexture(GL_TEXTURE0 + texture_unit_index);
-            DoCopyTexImage(texture, textarget, image);
+            if (image->BindTexImage(textarget)) {

[sandersd (OOO until July 31), 2017/05/23 23:23:31]

This is same as the core of DoCopyTexImageIfNeeded(). Can
DoCopyTexImageIfNeeded() be reduce or refactored to share the implementation?

+              image_state = Texture::BOUND;
+            } else {
+              DoCopyTexImage(texture, textarget, image);
+            }
+            textures_set = true;
             continue;
           }
         }