content_shell_lib is marked "testonly", so targets that depend on it must also be "testonly" (for example, app_shell via //extensions/shell:app_shell_lib).

Apparently, a bunch of test support is compiled into content_shell, and content_shell itself depends on testonly targets like:

    "//components/test_runner:test_runner",
    "//content/test:content_test_mojo_bindings",
    "//content/test:layouttest_support",
    "//content/test:test_support",
    "//testing/gmock",
    "//testing/gtest",
    "//third_party/WebKit/public:test_support",

Some of this code executes behind the --run-layout-test switch via switches::IsRunLayoutTestSwitchPresent(), which has a TODO for this in shell_switches.h[1].

content/shell/browser/shell.cc has several calls to switches::IsRunLayoutTestSwitchPresent() and #includes a bunch of files in content/shell/browser/layout_test.

Because AppShell -- which we hope to start shipping to some clients in the near future -- uses content_shell_lib, it includes all this test support, too.

Can we move these test dependencies to a separate target, either by #ifdefs in the //content code that does test stuff, or by moving this test stuff out of those files? Is there a good reason not to?

[1] https://cs.chromium.org/chromium/src/content/shell/common/shell_switches.h?type=cs&q=todo&sq=package:chromium&l=27