Implement GetInstalledFile() in WidevineCdmComponentInstaller.

chrome/browser/component_updater/widevine_cdm_component_installer.cc

Index: chrome/browser/component_updater/widevine_cdm_component_installer.cc
diff --git a/chrome/browser/component_updater/widevine_cdm_component_installer.cc b/chrome/browser/component_updater/widevine_cdm_component_installer.cc
index 8bc3feff3eb36b62cbff0a79e7057ef370cc35b2..a4cbe48b741f398d0bea2fd966729973cbdf2d77 100644
--- a/chrome/browser/component_updater/widevine_cdm_component_installer.cc
+++ b/chrome/browser/component_updater/widevine_cdm_component_installer.cc
@@ -251,7 +251,23 @@ bool WidevineCdmComponentInstaller::Install(
 
 bool WidevineCdmComponentInstaller::GetInstalledFile(
     const std::string& file, base::FilePath* installed_file) {
-  return false;
+  // Only the CDM is component updated.

[ddorwin, 2013/06/21 17:54:49]

tiny nit: component-updated

[xhwang, 2013/06/21 18:16:54]

Done.

+  if (file != kWidevineCdmFileName)
+    return false;
+
+  // No CDM has been installed yet.

[ddorwin, 2013/06/21 17:54:49]

This reads as a fact when it should describe the check (or be above "return
false;"

[xhwang, 2013/06/21 18:16:54]

Done.

+  if (current_version_.Equals(base::Version(kNullVersion)))
+    return false;
+
+  base::FilePath installed_cdm_path =
+      GetWidevineCdmBaseDirectory().AppendASCII(current_version_.GetString())
+          .AppendASCII(kWidevineCdmFileName);
+
+  // Ideally we should check if PathExists(installed_cdm_path) here. But this

[ddorwin, 2013/06/21 17:54:49]

What are the other implementations doing?
Maybe the GetInstalledFile interface description should explain that "true"
means I have a filename but don't know if it exists or is valid. I assume the
differential updater will check that.

[xhwang, 2013/06/21 18:16:54]

I think I am the first one implementing this :)

Sorin@: What do you think on this? I suppose the updater will check the path
returned by this method, correct?

[waffles, 2013/06/21 18:23:24]

We will have a failure with a more specific error code later if GetInstalledFile
returns true with a path that doesn't point to a file, or a path that has a file
with a different CRC than we expect, so we don't consider it the installer's
responsibility to verify that the file is as it should be.

This function is just a name mapping function. There does not need to be any
verification done at this step.

I agree with ddorwin that the interface description should be expanded to detail
this.

By the way, we expect to call this on the "FILE" thread.

+  // thread does not allow IO.
+
+  *installed_file = installed_cdm_path;
+  return true;
 }
 
 void FinishWidevineCdmUpdateRegistration(ComponentUpdateService* cus,