Let DoMapBufferRange write the result integer to signal a GL error.

gpu/command_buffer/service/gles2_cmd_decoder_passthrough_handlers.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder_passthrough_handlers.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_handlers.cc b/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_handlers.cc
index a1398ed00face271b0ae54410cde388f2c2989b6..46b0f571b675c9d4edc1f46886a0e3baa0376080 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_handlers.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_handlers.cc
@@ -1322,13 +1322,14 @@ error::Error GLES2DecoderPassthroughImpl::HandleMapBufferRange(
     return error::kOutOfBounds;
   }
 
-  error::Error error = DoMapBufferRange(target, offset, size, access, mem,
-                                        c.data_shm_id, c.data_shm_offset);
+  error::Error error =
+      DoMapBufferRange(target, offset, size, access, mem, c.data_shm_id,
+                       c.data_shm_offset, result);
   if (error != error::kNoError) {
+    DCHECK(*result == 0);
     return error;
   }
 
-  *result = 1;
   return error::kNoError;
 }