Add Widevine CDM support (issue #1631)

- Windows/Mac: Use `--enable-widevine-cdm` command-line flag to
  enable download of CDM binaries via the component updater.
- Linux: Use `--widevide-cdm-path` and `--widevine-cdm-version`
  command-line flags to load CDM binaries that already exist on
  the system.
- A cache-path value is usually required when CDM is enabled.

libcef/browser/context.cc

@@ -9,6 +9,7 @@
 #include "libcef/browser/browser_main.h"
 #include "libcef/browser/browser_message_loop.h"
 #include "libcef/browser/chrome_browser_process_stub.h"
+#include "libcef/browser/component_updater/cef_component_updater_configurator.h"
 #include "libcef/browser/content_browser_client.h"
 #include "libcef/browser/thread_util.h"
 #include "libcef/browser/trace_subscriber.h"
@@ -22,7 +23,11 @@
 #include "base/debug/debugger.h"
 #include "base/files/file_util.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/threading/thread_restrictions.h"
+#include "chrome/browser/component_updater/widevine_cdm_component_installer.h"
 #include "chrome/browser/printing/print_job_manager.h"
+#include "components/component_updater/component_updater_service.h"
+#include "components/update_client/configurator.h"
 #include "content/public/app/content_main.h"
 #include "content/public/app/content_main_runner.h"
 #include "content/public/browser/notification_service.h"
@@ -330,6 +335,23 @@ CefTraceSubscriber* CefContext::GetTraceSubscriber() {
   return trace_subscriber_.get();
 }
 
+component_updater::ComponentUpdateService*
+CefContext::component_updater() {
+  if (!component_updater_.get()) {
+    CEF_REQUIRE_UIT_RETURN(NULL);
+    scoped_refptr<update_client::Configurator> configurator =
+        component_updater::MakeCefComponentUpdaterConfigurator(
+            base::CommandLine::ForCurrentProcess(),
+            CefContentBrowserClient::Get()->browser_context()->
+                request_context().get());
+    // Creating the component updater does not do anything, components
+    // need to be registered and Start() needs to be called.
+    component_updater_.reset(component_updater::ComponentUpdateServiceFactory(
+                                 configurator).release());
+  }
+  return component_updater_.get();
+}
+
 void CefContext::PopulateRequestContextSettings(
     CefRequestContextSettings* settings) {
   CefRefPtr<CefCommandLine> command_line =
@@ -345,12 +367,31 @@ void CefContext::PopulateRequestContextSettings(
       CefString(&settings_.accept_language_list);
 }
 
+void RegisterComponentsForUpdate() {
+  component_updater::ComponentUpdateService* cus =
+      CefContext::Get()->component_updater();
+
+  // Registration can be before or after cus->Start() so it is ok to post
+  // a task to the UI thread to do registration once you done the necessary
+  // file IO to know you existing component version.
+#if !defined(OS_CHROMEOS) && !defined(OS_ANDROID)
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableWidevineCdm)) {
+    RegisterWidevineCdmComponent(cus);
+  }
+#endif  // !defined(OS_CHROMEOS) && !defined(OS_ANDROID)
+}
+
 void CefContext::OnContextInitialized() {
   CEF_REQUIRE_UIT();
 
   // Must be created after the NotificationService.
   print_job_manager_.reset(new printing::PrintJobManager());
 
+  bool io_was_allowed = base::ThreadRestrictions::SetIOAllowed(true);
+  RegisterComponentsForUpdate();
+  base::ThreadRestrictions::SetIOAllowed(io_was_allowed);
+
   // Notify the handler.
   CefRefPtr<CefApp> app = CefContentClient::Get()->application();
   if (app.get()) {