Remove RuntimeAPIDelegate::GetPreviousVersion.

extensions/browser/extension_registry.h

Index: extensions/browser/extension_registry.h
diff --git a/extensions/browser/extension_registry.h b/extensions/browser/extension_registry.h
index 81bb6f5bef538ecc9f9dab3ebb8355a549edce96..e5a6e08b9f873035d337dcbf9e888571cb92967d 100644
--- a/extensions/browser/extension_registry.h
+++ b/extensions/browser/extension_registry.h
@@ -20,6 +20,10 @@
 #error "Extensions must be enabled"
 #endif
 
+namespace base {
+class Version;

[Devlin, 2017/05/19 02:04:01]

nit: Since we return a non-pointer for base::Version, don't we need to include
version.h?  (I'm suspecting it's transitively included right now)

[lazyboy, 2017/05/19 18:24:55]

Yes, fixed.

+}
+
 namespace content {
 class BrowserContext;
 }
@@ -82,6 +86,15 @@ class ExtensionRegistry : public KeyedService {
   std::unique_ptr<ExtensionSet> GenerateInstalledExtensionsSet(
       int include_mask) const;
 
+  // Returns the current version of the extension.
+  // Note that if we are in the process of updating the extension, this will
+  // return the version before update.
+  //
+  // TODO(lazyboy): Consider updating callers to directly retrieve version()
+  // from either GetExtensionById() or querying ExtensionSet getters of this
+  // class.
+  base::Version GetVersion(const Extension* extension) const;

[Devlin, 2017/05/19 02:04:00]

Without the context of this patch, it's *very* why this is different than
calling Extension::version() on the passed-in extension.

What if do something like:
// Returns the current version of the extension with the given |id|, if
// one exists.
// Note: If we are currently updating the extension, this returns the
// version stored currently, rather than the in-progress update.
base::Version GetStoredVersion(const ExtensionId& id);

WDYT?

[lazyboy, 2017/05/19 18:24:55]

GetStoredVersion is definitely better than GetVersion, which would have kept
readers guessing, thanks!

+
   // The usual observer interface.
   void AddObserver(ExtensionRegistryObserver* observer);
   void RemoveObserver(ExtensionRegistryObserver* observer);