widevine: Use component updater with the Alloy runtime (fixes issue #3149)

Widevine CDM binaries will be downloaded on supported platforms shortly after
application startup. Widevine support will then become available within a few
seconds after successful installation on Windows or after the next application
restart on other platforms. The CDM files will be downloaded to a "WidevineCdm"
directory inside the `CefSettings.user_data_path` directory.

Pass the `--disable-component-update` command-line flag to disable Widevine
download and installation. Pass the `--component-updater=fast-update` command-
line flag to force Widevine download immediately after application startup.

See the related issue for additional usage details.

libcef/browser/web_plugin_impl.cc

@@ -6,7 +6,6 @@
 
 #include "libcef/browser/context.h"
 #include "libcef/browser/thread_util.h"
-#include "libcef/common/widevine_loader.h"
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
@@ -30,23 +29,6 @@ void PluginsCallbackImpl(
   }
 }
 
-#if !(BUILDFLAG(ENABLE_WIDEVINE) && BUILDFLAG(ENABLE_LIBRARY_CDMS)) || \
-    defined(OS_LINUX)
-
-void DeliverWidevineCdmError(const std::string& error_message,
-                             CefRefPtr<CefRegisterCdmCallback> callback) {
-  LOG(ERROR) << error_message;
-  if (callback.get()) {
-    CEF_POST_TASK(
-        CEF_UIT,
-        base::BindOnce(&CefRegisterCdmCallback::OnCdmRegistrationComplete,
-                       callback.get(), CEF_CDM_REGISTRATION_ERROR_NOT_SUPPORTED,
-                       error_message));
-  }
-}
-
-#endif
-
 }  // namespace
 
 // CefWebPluginInfoImpl
@@ -166,24 +148,3 @@ void CefIsWebPluginUnstable(const CefString& path,
                   base::BindOnce(CefIsWebPluginUnstable, path, callback));
   }
 }
-
-void CefRegisterWidevineCdm(const CefString& path,
-                            CefRefPtr<CefRegisterCdmCallback> callback) {
-#if BUILDFLAG(ENABLE_WIDEVINE) && BUILDFLAG(ENABLE_LIBRARY_CDMS)
-#if defined(OS_LINUX)
-  // Enforce the requirement that CefRegisterWidevineCdm() is called before
-  // CefInitialize() on Linux. See comments in
-  // CefWidevineLoader::AddPepperPlugins for details.
-  if (CONTEXT_STATE_VALID()) {
-    DeliverWidevineCdmError(
-        "Widevine registration is not supported after context initialization",
-        callback);
-    return;
-  }
-#endif  // defined(OS_LINUX)
-
-  CefWidevineLoader::GetInstance()->LoadWidevineCdm(path, callback);
-#else
-  DeliverWidevineCdmError("Widevine registration is not supported", callback);
-#endif  // BUILDFLAG(ENABLE_WIDEVINE) && BUILDFLAG(ENABLE_LIBRARY_CDMS)
-}