fix sign-compare warning.

content/common/gpu/media/video_encode_accelerator_unittest.cc

Index: content/common/gpu/media/video_encode_accelerator_unittest.cc
diff --git a/content/common/gpu/media/video_encode_accelerator_unittest.cc b/content/common/gpu/media/video_encode_accelerator_unittest.cc
index 56d40a240c5fe261c39b27e2d60c82fad134529a..e6d4a1707d885be2901ebecaa84226ddd31e9467 100644
--- a/content/common/gpu/media/video_encode_accelerator_unittest.cc
+++ b/content/common/gpu/media/video_encode_accelerator_unittest.cc
@@ -594,7 +594,7 @@ void VEAClient::RequireBitstreamBuffers(unsigned int input_count,
   // performance testing. So just assert that the frame size is a multiple of
   // 64 bytes. This ensures all frames start at 64-byte boundary, because
   // MemoryMappedFile should be mmapp()ed at virtual page start as well.
-  ASSERT_EQ(input_buffer_size_ & 63, 0)
+  ASSERT_EQ(input_buffer_size_ & 63, 0u)
       << "Frame size has to be a multiple of 64 bytes";
   ASSERT_EQ(reinterpret_cast<off_t>(test_stream_.input_file.data()) & 63, 0)
       << "Mapped file should be mapped at a 64 byte boundary";