Cherry pick PR #2205: Fix uninitialized variable append_ in class constructors #1615

Job	Run time
raspi-2 / initialize	48s
raspi-2-skia / initialize	35s
raspi-2-skia / docker-build-image	24s
raspi-2-skia / docker-unittest-image	0s
raspi-2 / docker-build-image	26s
raspi-2 / docker-unittest-image	0s
raspi-2-skia / raspi-2-skia_devel	8m 25s
raspi-2-skia / raspi-2-skia_debug	10m 56s
raspi-2-skia / raspi-2-skia_qa	7m 3s
raspi-2-skia / raspi-2-skia_gold	7m 26s
raspi-2 / raspi_devel	8m 5s
raspi-2 / raspi_debug	11m 27s
raspi-2 / raspi_qa	6m 58s
raspi-2 / raspi_gold	7m 7s
raspi-2 / sbversion-15_devel	8m 6s
raspi-2 / sbversion-15_debug	11m 19s
raspi-2 / sbversion-15_qa	6m 55s
raspi-2 / sbversion-15_gold	7m 11s
raspi-2-skia / ${{ matrix.name }}_${{ matrix.shard }}_test	0s
raspi-2-skia / ${{ matrix.name }}_on_device_${{ matrix.shard }}	0s
raspi-2-skia / on-host-unit-test-report	0s
raspi-2 / ${{ matrix.name }}_${{ matrix.shard }}_test	0s
raspi-2 / ${{ matrix.name }}_on_device_${{ matrix.shard }}	0s
raspi-2 / on-host-unit-test-report	0s
	1h 43m 11s

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