Replace the use of CLD_DATA_FROM* and CLD-related ifdefs with runtime checks.

chrome/browser/component_updater/cld_component_installer.cc

Index: chrome/browser/component_updater/cld_component_installer.cc
diff --git a/chrome/browser/component_updater/cld_component_installer.cc b/chrome/browser/component_updater/cld_component_installer.cc
index e922479acf1aeb247793220726ca8597dbd8414a..61be9732d67ca6f6704f6ba276f10f11cd33c37a 100644
--- a/chrome/browser/component_updater/cld_component_installer.cc
+++ b/chrome/browser/component_updater/cld_component_installer.cc
@@ -15,6 +15,7 @@
 #include "base/path_service.h"
 #include "components/component_updater/component_updater_paths.h"
 #include "components/translate/content/browser/browser_cld_data_provider.h"
+#include "components/translate/content/common/cld_data_source.h"
 #include "content/public/browser/browser_thread.h"
 #include "net/ssl/ssl_config_service.h"
 
@@ -105,6 +106,15 @@ std::string CldComponentInstallerTraits::GetName() const {
 }
 
 void RegisterCldComponent(ComponentUpdateService* cus) {
+  // Make sure we don't start up if the CLD data source isn't compatible.

[Sorin Jianu, 2014/07/29 18:04:47]

I wonder if the new code can be refactored and implemented in the CLD module, so
the code in the component updater here looks like:

void RegisterCldComponent(ComponentUpdateService* cus) {
 if (!translate::CldDataSource::CanRegisterForUpdates())
   return false;
 ...
}

The idea is that we want to avoid seeing implementation details such as the name
of the data source. Plus, we can do extra validation, record UMA stats, etc if
the check is implemented on the CLD side.

+  if (translate::CldDataSource::GetName() != "component") {

[Sorin Jianu, 2014/07/29 18:04:47]

Do we have concerns re: hard coded literal "component" ?

+    // This is a serious build-time configuration error.
+    LOG(ERROR) << "Wrong CLD data source: " <<

[jochen (gone - plz use gerrit), 2014/07/29 15:30:01]

why not LOG(FATAL)?

+        translate::CldDataSource::GetName();
+    NOTREACHED();
+    return;
+  }
+
   // This log line is to help with determining which kind of provider has been
   // configured. See also: chrome://translate-internals
   VLOG(1) << "Registering CLD component with the component update service";