Cherrypick "Don't include TargetConditionals.h when building for android."

> Move the include of the Mac TargetConditionals.h file to after we've
> checked if we're building for Android. Apparently this file doesn't
> exist on all macs used to build android and the rest of android builds
> fine without it, so including it there causes the build to fail. It
> appears to only be used to test TARGET_OS_IPHONE which will never be
> true on android.
>
> BUG=
>
> Review URL: https://codereview.chromium.org/538563002
>
> Cr-Commit-Position: refs/heads/master@{#293495}

Bug: 17401514
1 file changed