Address review comments from @aacid

Adding const for local variables, scope for one switch case to
reintroduce named variable, no multplication by boolean.
7 jobs for fill_bitmap_helpers in 4 minutes and 32 seconds (queued for 4 seconds)
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Status Job ID Name Coverage
  Build
passed #4323922
build

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passed #4323927
build_android

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passed #4323923
build_clang_libcpp

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passed #4323926
build_clazy

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passed #4323925
build_mingw64_fedora

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passed #4323924
build_ubuntu_16_04

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passed #4323921
clang_format

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