Reland of Enable whitelist generation for official builds.

Previous: https://codereview.chromium.org/2271673002/

Currently, all resources are included in PAK files when Chrome is
built locally. Only official_buildbot.sh uses a resource whitelist. This
CL enables local builds to use resource whitelisting by setting the
enable_resource_whitelist_generation gn flag to true, or by building an
official build.

This will allow developers to more easily monitor the changes in APK
size for each commit they make.

However, a large amount of output is generated (_pragma is used to
create warnings to allow whitelisted resources to be listed), so for now
the whitelist will only be generated for official builds.

This change results in a ~1.5 mb difference when calculating the APK
size with resource_sizes.py.

BUG=632385

Review-Url: https://codereview.chromium.org/2272713004
Cr-Commit-Position: refs/heads/master@{#414148}
14 files changed