About 1.5% of load.php wall-time is spent in isFileModule() calls
during the ServiceWiring/getResourceLoader/register call early on.
Reduce the overhead of this cost by moving that logic to the Module
class.
There are two costs that we save this way:
1. The inherent cost of applying the skinStyles.
This is now limited to only the modules that are constructed in a
given web request. Thus, apart from the startup response (which
constructs all modules), for regular load.php requests and all
index.php page views, the vast majority of modules will never need
to be constructed, and thus won't pay this cost.
2. The overhead of predicting (and class-loading) for whether a module
is (or will become) a FileModule object.
This is what isFileModule() does and is the main reason I wrote
this patch. It involves class loading, and checks and conditions that
run 1000+ times at WMF. This is eliminated now because we no longer
have to calculate this decision. Instead, the logic applies when
it needs to (due to FileModule implementing it), and doesn't
when it doesn't!
Change-Id: Ia2db14f930800c96e767b94ef62fb00e9d52725b
1367e356e7