BrowserMediaPlayerManager manages MediaKeys objects.
Changes in this CL:
- Add cdm_factory.h to support platform specific CDM creation.
- Detach BrowserMediaPlayerManager from MediaDrmBridge.
- Store the security origin of CDMs in the manager so that CDMs don't need to
know it.
- Keep the CDM ID in the manager so that CDMs don't see it.
BUG=338910
TEST=Test page plays and tests still pass.
Review URL: https://codereview.chromium.org/
276973005
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271034 0039d316-1c4b-4281-b951-d872f2087c98