A prerender process may be shared across two (or more)
extensions when Chrome reaches prerender process limit. In
this case, extensions' main worlds use the same Activity
Logger (which is defined by whoever sets it first); thus
producing incorrect extension ID in AL entries for
extensions.

This fix changes the way we locate Activity Logger for the
main world of an extension. Now, the extension ID is
required to locate the appropriate Activity Logger. Note, it
is only required for the main world not an isolated world.

Note: this CL contains contains stubs that allow
modifications to Chromium. After the Chromium modifications,
the stubs must be removed.

BUG=366916

Review URL: https://codereview.chromium.org/257803006

git-svn-id: svn://svn.chromium.org/blink/trunk@175381 bbb929c8-8fbe-4397-9dbb-9b2b20218538