command buffer: tweak error messages for a few more ES3 commands

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 bd7bed5278f045b9e79c7fbbed2eba291918d3fc..e4d664d01b0d94bfb0e3b3ce1db0fc9b39d5f7a2 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -15278,6 +15278,7 @@ error::Error GLES2DecoderImpl::HandleGetTransformFeedbackVarying(
   Program* program = GetProgramInfoNotShader(
       program_id, "glGetTransformFeedbackVarying");
   if (!program) {
+    // An error is already set.
     return error::kNoError;
   }
   GLuint service_id = program->service_id();
@@ -17212,6 +17213,7 @@ error::Error GLES2DecoderImpl::HandleClientWaitSync(
     case GL_CONDITION_SATISFIED:
       break;
     case GL_WAIT_FAILED:
+      NOTREACHED();

[Zhenyao Mo, 2016/11/01 02:27:48]

This could happen in context lost.

[Kai Ninomiya, 2016/11/01 03:16:01]

Ah, okay. Is it okay that it returns kNoError in this case, then?

[Zhenyao Mo, 2016/11/01 04:49:44]

I think the LOSE_CONTEXT gl error will be handled somewhere, but if you want to
return kContextLost, that's fine too.

[Kai Ninomiya, 2016/11/01 20:28:42]

Done.

       // Avoid leaking GL errors when using virtual contexts.
       LOCAL_PEEK_GL_ERROR(function_name);
       break;
@@ -17389,12 +17391,13 @@ error::Error GLES2DecoderImpl::HandleMapBufferRange(
     return error::kNoError;
   }
   if (size == 0) {
-    LOCAL_SET_GL_ERROR(GL_INVALID_OPERATION, func_name, "size is zero");
+    LOCAL_SET_GL_ERROR(GL_INVALID_OPERATION, func_name, "length is zero");
     return error::kNoError;
   }
   Buffer* buffer = buffer_manager()->RequestBufferAccess(
       &state_, target, offset, size, func_name);
   if (!buffer) {
+    // An error is already set.
     return error::kNoError;
   }
   if (state_.bound_transform_feedback->active() &&
@@ -17425,7 +17428,7 @@ error::Error GLES2DecoderImpl::HandleMapBufferRange(
   }
   if (!AnyBitsSet(access, GL_MAP_READ_BIT | GL_MAP_WRITE_BIT)) {
     LOCAL_SET_GL_ERROR(GL_INVALID_OPERATION, func_name,
-        "neither MAP_READ_BIT nore MAP_WRITE_BIT is set");
+        "neither MAP_READ_BIT nor MAP_WRITE_BIT is set");
     return error::kNoError;
   }
   if (AllBitsSet(access, GL_MAP_READ_BIT) &&
@@ -17433,7 +17436,7 @@ error::Error GLES2DecoderImpl::HandleMapBufferRange(
                           GL_MAP_INVALIDATE_BUFFER_BIT |
                           GL_MAP_UNSYNCHRONIZED_BIT))) {
     LOCAL_SET_GL_ERROR(GL_INVALID_OPERATION, func_name,
-        "Incompatible access bits with MAP_READ_BIT");
+        "incompatible access bits with MAP_READ_BIT");
     return error::kNoError;
   }
   if (AllBitsSet(access, GL_MAP_FLUSH_EXPLICIT_BIT) &&
@@ -17457,6 +17460,8 @@ error::Error GLES2DecoderImpl::HandleMapBufferRange(
   }
   void* ptr = glMapBufferRange(target, offset, size, access);
   if (ptr == nullptr) {
+    // This should mean GL_OUT_OF_MEMORY.

[Kai Ninomiya, 2016/11/01 03:16:01]

Can context loss (or anything else) trigger this? If this is always supposed to
be GL_OUT_OF_MEMORY, maybe it can be DCHECKed here.

[Zhenyao Mo, 2016/11/01 04:49:44]

In context lost, the behavior (returned value) is undefined.

[Kai Ninomiya, 2016/11/01 20:28:41]

Done.

+    LOCAL_COPY_REAL_GL_ERRORS_TO_WRAPPER(func_name);
     return error::kNoError;
   }
   buffer->SetMappedRange(offset, size, access, ptr,