ImageCapture: replace Mojo String/Array with stl/wtf string/vector

This CL nukes the usage of mojo::String and mojo::Array<> after [1],
so where it was mojo::String it now reads std::string or WTF::String
and also mojo::Array<> is replaced with std::vector or WTF::Vector,
as appropriate.

[1] https://groups.google.com/a/chromium.org/forum/?utm_medium=email&utm_source=footer#!msg/chromium-mojo/2SHvKyahLGg/sU61P0IIBgAJ

BUG=624136, 518807

TBR=xhwang@chromium.org
for the trivial change in media/mojo/interfaces/BUILD.gn

Review-Url: https://codereview.chromium.org/2166713002
Cr-Commit-Position: refs/heads/master@{#406776}
12 files changed