Remove extensions::util::GetSiteForExtensionId().

Removing GetSiteForExtensionId() and updated the sole caller since it
doesn't actually need to use a site URL to accomplish what it was
trying to do.

- Removed extensions::util::GetSiteForExtensionId() to discourage new
  usage of site URLs.
- Updated file system logic to compute the origin it needs directly
  from the extension URL instead of calling GetSiteForExtensionId() to
  indirectly generate the same URL.

Bug: 1085275
Change-Id: I501e6ab3596597e4cdd8ee28df2c91f1104bed1f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2339608
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Auto-Submit: Aaron Colwell <acolwell@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795615}

extensions/browser/api/file_system/file_system_api.cc

@@ -828,10 +828,10 @@ ExtensionFunction::ResponseAction FileSystemRetainEntryFunction::Run() {
         util::GetStoragePartitionForExtensionId(extension_id(),
                                                 browser_context())
             ->GetFileSystemContext();
-    const GURL origin =
-        util::GetSiteForExtensionId(extension_id(), browser_context());
+
     const storage::FileSystemURL url = context->CreateCrackedFileSystemURL(
-        url::Origin::Create(origin), storage::kFileSystemTypeIsolated,
+        url::Origin::Create(extension()->url()),
+        storage::kFileSystemTypeIsolated,
         storage::IsolatedContext::GetInstance()
             ->CreateVirtualRootPath(filesystem_id)
             .Append(base::FilePath::FromUTF8Unsafe(filesystem_path)));

extensions/browser/extension_util.cc

@@ -79,14 +79,6 @@ bool CanCrossIncognito(const Extension* extension,
          !IncognitoInfo::IsSplitMode(extension);
 }
 
-GURL GetSiteForExtensionId(const std::string& extension_id,
-                           content::BrowserContext* context) {
-  GURL site = content::SiteInstance::GetSiteForURL(
-      context, Extension::GetBaseURLFromExtensionId(extension_id));
-  DCHECK_EQ(extension_id, site.host());
-  return site;
-}
-
 const std::string& GetPartitionDomainForExtension(const Extension* extension) {
   // Extensions use their own ID for a partition domain.
   return extension->id();

extensions/browser/extension_util.h

@@ -42,11 +42,6 @@ bool IsIncognitoEnabled(const std::string& extension_id,
 bool CanCrossIncognito(const extensions::Extension* extension,
                        content::BrowserContext* context);
 
-// Returns the site of the |extension_id|, given the associated |context|.
-// Suitable for use with BrowserContext::GetStoragePartitionForSite().
-GURL GetSiteForExtensionId(const std::string& extension_id,
-                           content::BrowserContext* context);
-
 // Returns the StoragePartition domain for |extension|.
 // Note: The reference returned has the same lifetime as |extension|.
 const std::string& GetPartitionDomainForExtension(const Extension* extension);