[iOS][GN] Port ios_web_unittests to build with gn

Add template to run a java command as an "script", i.e. templates
java_action/java_action_foreach similar to action/action_foreach.

Add template to compile a bunch of JavaScript to a bundle and to
compile JavaScript files with closure compile (only enable checks
that are known to work).

Fix gcdwebserver public configuration to add the dependency on libz
to libs instead of using ldflags.

Add files missing from //ui/base:test_support when building for iOS
with gn (they are present in the gyp build).

BUG=459705

Review URL: https://codereview.chromium.org/1393303003

Cr-Commit-Position: refs/heads/master@{#355460}

• BUILD.gn[diff]
• build/util/java_action.gni[Added - diff]
• build/util/java_action.py[Added - diff]
• ios/third_party/gcdwebserver/BUILD.gn[diff]
• ios/web/BUILD.gn[Added - diff]
• ios/web/ios_web.gyp[diff]
• ios/web/ios_web_unittests.gyp[diff]
• ios/web/js_compile.gni[Added - diff]
• ui/base/BUILD.gn[diff]