Fix incorrect buffer size DCHECK when copying scratch parameters.

Replace '<' with '<=', this was not found until recently because it
required that the result was being copied into the exact last element of
a much larger buffer.

BUG=874402
TBR=piman@chromium.org

Change-Id: Ib35552f331f0d9f1f1d19aa4914d1d14ec75ee2d
Reviewed-on: https://chromium-review.googlesource.com/c/1344214
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609874}

gpu/command_buffer/service/gles2_cmd_decoder_passthrough.h

@@ -399,7 +399,7 @@ class GPU_GLES2_EXPORT GLES2DecoderPassthroughImpl : public GLES2Decoder {
     }
 
     // Copy into the destination
-    DCHECK(*length < bufsize);
+    DCHECK(*length <= bufsize);
     std::copy(scratch_params, scratch_params + *length, params);
 
     return error::kNoError;